BBTX Bambusa Therapeutics, Inc. S-1/A amended IPO prospectus section summaries

Cover page and offering

Bambusa Therapeutics, Inc. filed Amendment No. 1 to its Form S-1 on October 26, 2026, for its proposed initial public offering. The company is offering 9,375,000 common shares at an indicated price range of $15.00–$17.00 per share, representing estimated gross proceeds of approximately $140.6–$159.4 million, before underwriting discounts and offering expenses.

The underwriters have a 30-day option to purchase up to 1,406,250 additional shares. If fully exercised, the offering would total 10,781,250 shares, with estimated gross proceeds of approximately $161.7–$183.3 million at the stated price range, before discounts and expenses. Up to 3.5% of the base offering shares are reserved for certain associated persons.

Listing and company status

No public market for Bambusa’s common stock existed before the offering. The company applied to list on the Nasdaq Global Select Market under the ticker BBTX; closing of the offering is contingent on approval of the listing. The prospectus is preliminary, and the final public offering price and net proceeds had not been specified.

Bambusa identifies as both an emerging growth company and a smaller reporting company, and has elected reduced public-company reporting requirements. This cover-page section provides no historical financial results or specific business risks; it directs investors to the prospectus’s Risk Factors section, beginning on page 16.

Bambusa Therapeutics — Prospectus Summary

Business and pipeline

Bambusa Therapeutics is a clinical-stage biopharmaceutical company incorporated in March 2024. It is developing long-acting bispecific antibodies for immunology and inflammation, aiming to combine complementary pathways in one molecule and enable high-concentration subcutaneous (SubQ) dosing. The company cites a projected global immunology and inflammation market exceeding $200B by 2030. Its business remains pre-commercial and dependent on successful clinical, regulatory, financing, and commercial execution.

• BBT001 (IL-4Rα/IL-31) is the lead program for moderate-to-severe atopic dermatitis (AD) and other inflammatory skin diseases, with development also underway in chronic spontaneous urticaria (CSU). In a four-week IV AD proof-of-concept study, July 2026 topline findings were based on 17 evaluable bio-naïve patients as of the June 8, 2026 cutoff; median follow-up was 71 days after first dose (range 33–165 days). The company reported statistically significant placebo-adjusted EASI improvement beginning at Week 1 and deepening through Week 6. At Week 6, placebo-adjusted EASI-50 and EASI-75 response proportions were 82% and 64%. It also reported itch improvement from Day 1, sustained for eight weeks after the last dose, and TARC and IgE reductions sustained for the same period. Tolerability was described as favorable, with no observed conjunctivitis and low-titer treatment-emergent anti-drug antibodies without apparent neutralizing activity. Pharmacology supports management’s belief that quarterly maintenance dosing may be feasible, but this is an expectation, not established practice.
• BBT002 (IL-4Rα/IL-5) targets Type 2 inflammatory respiratory and allergic diseases, including COPD, chronic rhinosinusitis with nasal polyps (CRSwNP), and asthma. Preliminary Phase 1 healthy-volunteer results included an estimated half-life of approximately 29 days, dose-dependent dual biomarker effects, TARC reduction and eosinophil depletion lasting more than eight weeks, and favorable safety and low immunogenicity. Management believes the findings may support quarterly maintenance dosing.
• BBT003, targeting TL1A and IL-23p19 for inflammatory bowel disease, is planned to enter clinical development by year-end 2026. BBT004, a dual B-cell depletion bispecific, is preclinical.

Expected first-half 2027 catalysts include BBT001 12-week IV AD studies in bio-naïve and bio-experienced patients and a 14-week IV CSU study; BBT002 four-week IV COPD and 12-week IV CRSwNP proof-of-concept results; and planned subsequent dose-ranging work. A BBT001 SubQ AD proof-of-concept substudy has begun dosing, and a SubQ asthma Phase 2a study of BBT002 has been initiated. These are forward-looking development plans; early, small-cohort findings do not establish later-stage efficacy, safety, durability, or approval.

Operating results and financial position

The financial statements report no revenue. Operating expenses and losses reflect the company’s development-stage operations.

H1 2026 total other income was $2.893M, versus $1.551M in H1 2025, including interest income of $1.313M versus $0.732M, and R&D incentives of $1.513M versus $1.236M. H1 2025 included a $0.454M fair-value expense for the preferred-stock tranche right obligation; H1 2026 had none. Net loss was $(22.360)M in H1 2026 versus $(14.747)M in H1 2025; the respective loss before tax was $(21.166)M versus $(13.897)M, and income-tax provisions were $1.194M versus $0.850M. FY 2025 net loss was $(41.087)M, versus $(13.741)M for the 2024 inception period. Net loss attributable to common stockholders was $(22.360)M in H1 2026, $(12.989)M in H1 2025, and $(39.332)M in FY 2025. Basic and diluted loss per share was $(2.56), $(2.30), and $(6.08), respectively.

At June 30, 2026, actual cash and cash equivalents were $46.534M, marketable securities $24.941M, working capital $63.076M, total assets $77.496M, total liabilities $12.223M, convertible preferred stock $136.231M, and stockholders’ deficit $(70.958)M. Goodwill and intangible assets other than goodwill are not presented in the summarized information. Operating cash flow and capital expenditures are also not provided.

Preliminary, unaudited September 30, 2026 cash, cash equivalents, and marketable securities were approximately $57.2M. Management said this would not fund operations for at least 12 months from financial-statement issuance and reported substantial doubt about the company’s ability to continue as a going concern.

Offering, dilution, and capital needs

The proposed IPO is 9,375,000 shares at an assumed midpoint of $16.00 per share, with an underwriters’ option for up to 1,406,250 additional shares. Estimated net proceeds are $134.9M, or $155.8M if the option is fully exercised. Pro forma shares outstanding are 49,761,875, or 51,168,125 with full exercise. At the assumed offering terms, pro forma as-adjusted cash would be $181.404M, working capital $199.690M, total assets $210.622M, liabilities $10.479M, and equity $200.143M. The company plans to use approximately $90M for BBT001, $40M for BBT002, and the remainder for BBT003/BBT004 development, capital expenditures, working capital, and public-company costs. It expects to need substantial additional capital even after the offering, with potential dilution or pressure to constrain operations or relinquish rights.

The post-offering share count includes conversion of 27,391,561 preferred shares and settlement of 621,192 liquidity-event RSUs (potentially up to 701,797 shares). The RSU settlement entails $10.0M of stock-based compensation, of which $9.4M is expected to be recognized upon offering close. Additional options, IPO awards, incentive-plan reserves, and automatic plan increases create further potential dilution.

Principal risks

Clinical outcomes are uncertain, and early or interim data may not predict later trials. Execution also relies on third-party trial operators, manufacturers and engineering technology, and protecting international intellectual property. Competition, trial delays or failures, regulatory requirements, commercial acceptance, pricing and reimbursement could limit the opportunity. The company has identified material weaknesses in internal control over financial reporting. It is an emerging growth company and smaller reporting company, uses reduced disclosure, and elected the extended transition period for new accounting standards.

BBTX — Risk Factors

Development, financing and commercialization

BBTX is a clinical-stage biotechnology company with a limited operating history, no approved products, and no product-sales or royalty revenue. At the prospectus date, BBT001 and BBT002 were in early clinical development; other candidates were preclinical, with the company aiming to advance BBT003. BBTX has never completed a pivotal trial, obtained regulatory approval, manufactured a commercial-scale product, or marketed a product. Its prospects therefore depend on uncertain development, regulatory approval, and eventual commercialization.

The company has incurred substantial losses and negative operating cash flows since formation. Net loss was $41.1 million in FY2025, versus $13.7 million from inception through December 31, 2024; H1 2026 net loss was $22.4 million, versus $14.7 million in H1 2025. Accumulated deficit was $77.2 million at June 30, 2026. BBTX has funded operations primarily with $136.1 million from convertible preferred stock. It had $71.5 million in cash, cash equivalents and marketable securities at June 30, 2026; including expected offering proceeds, management estimated funding into late 2028. That estimate depends on assumptions, and funds will not carry all candidates through approval. Management identified substantial doubt about the company’s ability to continue as a going concern for the 12 months after the audited financial statements were available to be issued. Further financing may be unavailable or unfavorable, and losses or cash needs could exceed expectations.

Additional equity could dilute holders; debt could add covenants or encumber assets; and partnerships or licenses could require surrendering valuable rights. Insufficient funding could force BBTX to delay, reduce, suspend, or abandon programs. Planned spending includes clinical trials, advancing the pipeline, regulatory work, manufacturing, IP protection, hiring, and public-company costs. The company also faces contingent BioNTech Zhuhai obligations, including up to $1.8 million in development milestones per program and, under a separate license, up to $6.9 million in development, $57.5 million in first-commercial-sale, and $217.5 million in sales milestones, plus low-single-digit royalties on licensed-product net sales.

Clinical failure, safety issues, weak or non-reproducible efficacy, enrollment delays, regulatory demands, or manufacturing problems could derail or delay programs even after promising early results. No serious adverse events had been observed in BBT001 and BBT002 studies as of their respective December 5, 2025 and January 19, 2026 data cutoffs, but later or broader testing may reveal safety concerns. Trial results may change as data are verified; accelerated approval, special FDA designations, or favorable results from other molecules do not assure approval for BBTX’s distinct candidates. Approval would still not assure adoption, adequate reimbursement, profitable pricing, or sufficient demand. Market estimates and the opportunity in competitive immunology and inflammation markets may prove overstated, while larger competitors may reach market first or offer more attractive treatments.

Operational, supply-chain and regulatory exposure

BBTX depends on CROs, investigators, clinical sites, and contract manufacturers for studies and clinical supply, limiting its direct control over execution and quality. Some providers and suppliers operate in China; WuXi Biologics performs the majority of IND-enabling CMC work for certain candidates, and other key relationships include BioNTech Zhuhai and Tigermed. Replacing a provider can require technology transfer, revalidation, added costs, or repeated studies. Disruptions, quality failures, capacity constraints, or noncompliance could delay trials or approvals and interrupt supply.

China-related geopolitical, trade, tariff, data-security, and regulatory restrictions—including the BIOSECURE Act and U.S. Data Security Program—could constrain existing or future arrangements. Moving work to alternative suppliers may itself cause delay and expense. International trials also introduce differing regulatory, data-integrity, privacy, labor, and trade requirements, and regulators may reject foreign data or require further studies.

Regulatory approval is uncertain and can require additional trials, narrow labels, post-market studies, warnings, or restricted distribution. Injectable candidates may be regulated as biologic-device combination products, adding review and manufacturing requirements. If approved, products would remain subject to extensive manufacturing, safety, promotion, and reporting rules. Pricing controls, reimbursement limits, Medicare negotiation and rebate policies, healthcare coverage changes, and fraud-and-abuse requirements could further constrain sales or increase compliance costs.

Intellectual property and partnerships

BBTX’s IP position is particularly immature: it owns or in-licenses no issued patents, and expects most patents from current applications not to issue for at least four years. Pending applications may be rejected or narrowed, and patents may not provide freedom to operate or survive third-party challenges. Patent protection could expire before or soon after commercialization; patent disputes, infringement claims, or difficulty obtaining third-party rights could delay or prevent development, impose damages or royalties, or require redesign or abandonment. Trade-secret loss, ownership disputes, and licensors’ control over prosecution or maintenance pose additional risks.

Development depends partly on BioNTech Zhuhai and potential future collaborators. Partners may underfund, delay, redirect, or terminate programs, while negotiations may be lengthy or yield unfavorable terms. A failed collaboration could cost BBTX funding, rights, milestones, and royalties, leaving it to raise capital or develop programs itself.

Public-company and shareholder risks

An audit identified material weaknesses in internal controls involving resources, journal-entry and reconciliation review, segregation of duties, and IT controls. Remediation is underway, but management and the auditor had not performed a Section 404 evaluation; ineffective controls could lead to reporting errors, restatements, regulatory action, or reduced market confidence. BBTX also faces cybersecurity and privacy risks involving sensitive clinical data and third-party systems, with breaches potentially causing operational disruption, litigation, penalties, and delayed development.

At the assumed $16.00 IPO price, purchasers would incur immediate dilution of $11.98 per share relative to pro forma as-adjusted net tangible book value per share. After the offering and specified conversions and settlement, BBTX expected 49,761,875 shares outstanding, including 9,375,000 shares sold by the company; substantial additional shares could become sale-eligible after lockups, potentially pressuring the stock. Insiders and significant holders were expected to retain approximately 65.8% of voting stock after the offering, giving them considerable influence. No liquid public market is assured, and clinical, financing, regulatory, or market developments could drive volatility. BBTX does not expect to pay dividends.

Other risks include its $13.3 million federal and $11.1 million state NOL carryforwards at December 31, 2025, whose use may be limited by ownership changes; dependence on key personnel; potential product-liability and litigation costs; and risks from public-company expenses and accounting estimates.

Forward-Looking Statements

The prospectus includes forward-looking statements about BioNTech Zhuhai’s clinical-stage product candidates and their safety and efficacy; clinical-trial progress and expected data timing; development plans; market potential; regulatory filings and approvals; commercialization, manufacturing, pricing and reimbursement; and competition. These expectations are uncertain, and actual results may differ materially, particularly in a rapidly changing and competitive environment where not all risks can be anticipated.

Important company-specific uncertainties include dependence on third parties for clinical trials and manufacturing; obtaining sufficient financing for operating and capital needs; securing favorable partnerships, collaborations, licenses, or out-licensing or sale arrangements; protecting intellectual property; and complying with the BioNTech Zhuhai license, including its development and commercial milestones. Other uncertainties include hiring and retaining personnel, remediating material weaknesses in internal control over financial reporting, regulatory developments, and the accuracy of estimates for expenses, revenue, capital requirements and cash runway. Forward-looking statements also address anticipated use of offering proceeds and the company’s expected status under the JOBS Act.

These statements reflect expectations and information available as of their stated dates. They are not guarantees or predictions and should not be relied on as assurances of future outcomes. The company generally undertakes no obligation to update them except as required by law. They also do not account for potential future acquisitions, mergers, dispositions, joint ventures or investments.

Market, Industry and Other Data

This section contains no financial metrics or operating results. Market-size and industry estimates are based on third-party publications and the company’s internal information. Some third-party sources are not specifically identified; the company has not independently verified third-party data, and its internal information has not been verified by an outside party.

The estimates depend on assumptions and have limitations. Industry uncertainty and related risks may cause actual conditions, including the size of the company’s addressable market, to differ materially from the estimates. Investors are cautioned not to place undue weight on them.

Use of IPO Proceeds

BBTX estimates net proceeds of approximately $134.9 million at an assumed offering price of $16.00 per share, rising to approximately $155.8 million if underwriters exercise their option in full. These estimates are net of underwriting discounts and commissions and offering expenses. At the base offering size, each $1.00 change in the IPO price would change net proceeds by approximately $8.7 million, while each 1.0 million-share change in the number of shares offered would change proceeds by approximately $14.9 million.

The company plans to allocate approximately $90.0 million to continued development of lead candidate BBT001, including initiation of a planned Phase 2b atopic dermatitis study, and approximately $40.0 million to BBT002, including an expected Phase 2b trial in a respiratory indication. Remaining proceeds are intended to support research and development of preclinical candidates BBT003 and BBT004, including advancing BBT003 into clinical development, as well as capital expenditures, working capital, and public-company costs. BBTX may also use proceeds for complementary licenses, acquisitions, or investments, although it had no specific agreements or commitments for these uses.

BBTX expects the offering proceeds, together with existing cash and cash equivalents and short-term investments, to fund operating expenses and capital expenditures into late 2028. This outlook depends on assumptions that may prove inaccurate; faster-than-expected cash consumption could require the company to seek additional financing sooner. Existing resources are not expected to fund all candidates through regulatory approval, and substantial additional capital will be needed. Management has broad discretion over proceeds, with actual spending dependent on research and clinical results, regulatory timing, potential collaborations, and unforeseen cash requirements. Until deployed, proceeds are expected to be held in short-term, interest-bearing investment-grade instruments.

The offering is intended to strengthen BBTX’s capitalization and financial flexibility, establish a public market for its shares, support future access to equity markets, and increase its market visibility.

BBTX has never declared or paid cash dividends and does not expect to do so in the foreseeable future. The company intends to retain available funds and future earnings to support operations and business growth. Any future dividend would be at the board’s discretion and depend on operating results, financial condition, contractual restrictions, and capital requirements. Future debt or preferred securities could impose additional restrictions on dividend capacity. No financial metrics are reported in this section.

Capitalization and proposed IPO

As of June 30, 2026, the company had $71.475 million in cash, cash equivalents and marketable securities. Actual capitalization included $136.231 million of convertible preferred stock and a $70.958 million stockholders’ deficit.

Assuming conversion of the preferred stock and settlement of liquidity-event RSUs, pro forma stockholders’ equity and total capitalization were $65.273 million. Pro forma accumulated deficit was $87.139 million, compared with $77.188 million actual. Common shares outstanding would increase from 12.374122 million actual to 40.386875 million pro forma before the offering.

The proposed IPO assumes the sale of 9.375 million common shares at $16.00 per share. Pro forma as adjusted, cash and marketable securities would be $206.345 million, while stockholders’ equity and total capitalization would be $200.143 million. The offering is expected to increase cash and equity by $134.870 million, after estimated underwriting discounts, commissions and offering expenses. Pro forma as-adjusted common shares outstanding would be 49.761875 million. These estimates are illustrative and depend on final offering terms. Each $1.00 change in IPO price would change cash, additional paid-in capital, equity and total capitalization by approximately $8.7 million; each 1.0 million-share change in offering size would change those amounts by approximately $14.9 million.

Potential dilution

The 40.386875 million pro forma pre-offering share count includes 2.866703 million unvested restricted shares. It excludes 1.550428 million options outstanding as of June 30, 2026, with a $0.90 weighted-average exercise price, and 1.621449 million options granted after that date, with a $12.66 weighted-average exercise price. It also excludes 0.379102 million IPO options exercisable at the IPO price, 0.758204 million IPO performance-based RSUs, and securities or other consideration potentially issuable upon settlement of outstanding VARs.

The 2026 Plan reserves 5.898951 million shares for future issuance, including the IPO options and IPO PSUs and 338,788 shares carried over from the 2024 Plan. The ESPP reserves an additional 0.505469 million shares. Both plans provide for automatic annual increases to their share reserves; the 2026 Plan may also receive shares from certain expired, forfeited or repurchased 2024 Plan awards. These provisions create further potential dilution beyond the pro forma as-adjusted share count.

Dilution

At the assumed IPO price of $16.00 per share (the midpoint of the indicated range), BBTX plans to issue 9,375,000 shares. Pro forma figures are based on June 30, 2026 and assume the preferred-stock conversion and Liquidity Event RSU settlement occurred on that date; adjusted tangible book value reflects estimated IPO proceeds after underwriting discounts, commissions, and offering expenses.

• Historical net tangible book deficit was $72.7 million, or $(5.88) per share.
• Before the offering, pro forma net tangible book value was $63.5 million, or $1.57 per share, after converting preferred stock into 27,391,561 common shares and issuing 621,192 shares for the Liquidity Event RSU settlement.
• After the offering, pro forma as-adjusted net tangible book value is $200.1 million, or $4.02 per share. This represents a $2.45 per-share increase over the pre-offering pro forma amount for existing holders, while IPO purchasers experience immediate dilution of $11.98 per share.
• Each $1.00 change in IPO price would change adjusted book value per share by $0.18 and investor dilution per share by $0.82, assuming the share count offered is unchanged. Each 1.0 million-share change in shares offered would change adjusted book value per share by approximately $0.21 if the offering increases or $0.22 if it decreases, with dilution moving inversely.
• If the underwriters exercise their 1,406,250-share option in full, adjusted book value is estimated at $4.32 per share, the increase to existing holders at $2.75 per share, and dilution to new investors at $11.68 per share, assuming the $16.00 IPO price.

At the assumed price and without the underwriters’ option, existing stockholders would hold 40,386,875 shares (81%), and IPO investors 9,375,000 shares (19%), for 49,761,875 shares outstanding. Before offering discounts and expenses, consideration is $136.078 million from existing holders (average $3.37 per share) and $150.0 million from new investors ($16.00 per share), totaling $286.078 million (average $5.75 per share). Full exercise of the option would reduce existing holders’ ownership to 79% and increase IPO investors’ ownership to 21%. These ownership figures exclude purchases by existing holders through the reserved-share program.

Potential additional dilution

The offering share count excludes 1,550,428 outstanding options as of June 30, 2026 (weighted-average exercise price $0.90) and 1,621,449 options granted afterward (weighted-average exercise price $12.66), as well as 379,102 IPO Options priced at the IPO price and 758,204 IPO PSUs. It also excludes 5,898,951 shares reserved under the 2026 Plan (including IPO Options and IPO PSUs), 505,469 shares reserved under the ESPP, and securities or other consideration potentially issuable for outstanding VARs. The plans provide for annual automatic increases in reserved shares; the 2026 Plan also absorbs certain unused 2024 Plan awards. BBTX may seek additional capital through equity or convertible debt even if it believes its operating needs are funded, and future issuances, conversions, option exercises, and equity awards could further dilute investors.

Business and pipeline

BBTX is a pre-revenue, clinical-stage biopharmaceutical company developing long-acting, high-concentration subcutaneous bispecific antibodies for immunology and inflammation (I&I). Its strategy is to combine validated biological pathways in one therapy for unmet needs across dermatology, respiratory, gastroenterology, and autoimmune diseases. The company cites a projected global I&I market exceeding $200B by 2030 as a market opportunity, not revenue guidance. It has no approved products and does not expect meaningful revenue unless candidates are approved and commercialized.

BBT001 (IL-4Rα/IL-31) and BBT002 (IL-4Rα/IL-5) were assigned by BioNTech Zhuhai with related research materials, data, and specified IP. BBTX must use commercially reasonable efforts to obtain IND approval for a lead candidate in each program; under specified circumstances, rights and regulatory materials can revert to BioNTech Zhuhai. BBT001 and BBT002 advanced through Phase 1b/2a trials, driving increased clinical-development spending.

Under a collaboration and option agreement, BBTX may nominate up to 10 target combinations through April 12, 2027, with BioNTech Zhuhai conducting discovery and preclinical work. BBTX licensed BBT003, a TL1A/IL-23p19 candidate, in September 2025 and has given notice exercising an option for BBT004. The BBT003 license requires IND approval by October 2027 and first Phase 2 patient dosing by October 2029, each with a 12-month extension right. Failure to meet obligations or other specified events can result in rights reverting. BBTX expects to advance BBT003 clinically and continue BBT004 research; later-stage trials, manufacturing, and reliance on CROs and CDMOs are expected to increase costs.

Agreements create potential future payments if programs advance: assigned-program milestones of up to approximately $1.8M in development and $11.0M in commercial milestones; BBT003 license obligations include a $57,500 annual fee until first commercial sale, up to $6.9M in development milestones, $57.5M at first commercial sale, $217.5M in sales milestones, and low-single-digit royalties. Adimab obligations include up to $3.0M in development milestones and $3.0M in marketing-approval milestones, plus low-single-digit royalties on certain products. Payments to BioNTech Zhuhai under the assignment agreement totaled approximately $4.8M through June 30, 2026, including $4.6M in FY2025 and $0.2M in 2024; none were made in H1 2026. BioNTech Zhuhai’s May 2026 nonrenewal of its Alloy license eliminated the $7,500 annual platform fee per assigned program.

Results, liquidity, and funding

BBTX has incurred no revenue and expects substantial further losses as it expands clinical development, manufacturing, hiring, pipeline work, and public-company operations. For the six months ended June 30, 2026 (H1 2026), R&D expense was $20.646M, up from $11.892M in H1 2025; G&A was $3.413M, down from $3.556M. Total operating expenses and operating loss were $24.059M versus $15.448M. Other income, net, rose to $2.893M from $1.551M; income tax provision was $1.194M versus $0.850M; net loss widened to $22.360M from $14.747M.

R&D growth reflected clinical advancement and manufacturing: BBT001 external costs were $6.636M versus $3.950M, BBT002 costs were $5.073M versus $3.097M, and early-program costs were $5.368M versus $0.448M, including $4.8M for BBT003 manufacturing development. Internal personnel costs declined to $3.428M from $3.738M, as a $1.9M reduction in stock-based compensation offset higher salaries and other personnel costs. G&A’s modest decline reflected lower stock compensation and professional-services costs, partly offset by headcount and public-company preparation.

In FY2025, R&D was $38.096M versus $13.025M from inception on March 14, 2024 through December 31, 2024; G&A was $5.910M versus $0.855M; operating expenses and operating loss were $44.006M versus $13.880M. Other income was $5.152M versus $0.139M, income tax provision was $2.233M versus zero, and net loss was $41.087M versus $13.741M (comparison periods differ in length). FY2025 R&D growth included $13.6M higher clinical-development costs, $4.4M higher manufacturing-development costs, and $5.4M higher personnel costs, including $2.6M of stock-based compensation. Higher other income included $3.3M of R&D incentive credit and $2.0M more interest income, partly offset by a $0.5M fair-value change in the preferred-stock tranche-right obligation.

Operating cash used was $20.137M in H1 2026 versus $19.040M in H1 2025, and $39.804M in FY2025 versus $4.634M from inception through December 31, 2024. H1 2026 cash use was below net loss, helped by $1.7M of working-capital changes and $0.6M of noncash charges. Investing cash provided $15.032M in H1 2026 versus zero in H1 2025, and used $39.728M in FY2025 versus zero in the 2024 inception period. Financing provided $0.996M versus $88.794M in H1 2026 and H1 2025, respectively, and $120.813M in FY2025 versus $13.996M in the inception period. H1 2026 investing inflow reflected $30.0M of marketable-security maturities less $15.0M of purchases.

Cash, cash equivalents, and marketable securities were $71.5M at June 30, 2026. The company reported substantial doubt about its ability to continue as a going concern because these resources were insufficient to fund operations for at least 12 months from issuance of the financial statements; its FY2025 auditor report also included an explanatory paragraph. Separately, BBTX estimated that existing resources plus anticipated net offering proceeds would fund operations into late 2028, subject to assumptions that may prove wrong. It had raised $136.1M gross through preferred-stock sales since inception. Additional capital is necessary; unavailable or unfavorable financing could force program reductions, delays, terminations, or licensing of rights. Equity would dilute shareholders; debt could impose covenants and senior repayment claims.

Other risks and reporting matters

BBTX’s common-stock valuations increased from $2.41/share in February 2025 to $13.57 in September 2026 as the modeled probability of an IPO increased. The company moved from an option-pricing method to a hybrid PWERM/OPM approach in April 2026; valuation assumptions affect stock-based compensation and reported loss. In October 2026, 701,797 cash-settled value appreciation rights were replaced with performance- and service-conditioned RSUs. At an assumed $16 IPO price, approximately 621,192 shares were estimated to vest, with $10.0M grant-date fair value.

BBTX identified material weaknesses in internal control over financial reporting for FY2025 and the 2024 inception period; failure to remediate could impair accurate or timely reporting. R&D accruals rely on estimates of vendor work and trial activity. The company has no formal foreign-currency hedging program, reports no off-balance-sheet arrangements, and CRO/CDMO contracts may require payment for completed services and certain noncancelable costs upon cancellation. It is an emerging growth company and smaller reporting company, with reduced disclosure and auditor-attestation requirements and the JOBS Act extended transition period for new accounting standards.

Business and Development Overview

Company strategy and platform

BBTX is a clinical-stage biopharmaceutical company, incorporated in March 2024, developing long-acting bispecific antibodies for immunology and inflammation (I&I). Its strategy is to combine complementary, clinically validated targets in one molecule, with the goal of addressing multiple disease pathways while enabling longer dosing intervals and high-concentration subcutaneous (SubQ) administration. The company estimates the I&I market exceeds $150 billion and could exceed $200 billion by 2030, with an estimated 6% CAGR for 2025–2030; these are industry estimates, not BBTX revenue or demonstrated addressable sales.

BBT001 and BBT002 use a tetravalent 2+2 antibody format; BBT003 and BBT004 use 1+1 formats. The lead candidates incorporate half-life engineering and are being developed with SubQ formulations. The company cites the related antibody architecture’s use in pumitamig, studied in more than 2,000 patients and in seven ongoing global Phase 3 trials, but emphasizes that pumitamig is a different molecule and does not establish BBTX candidates’ safety or efficacy.

Lead clinical programs

BBT001 targets IL-4Rα and IL-31, intended to combine control of Type 2 inflammation with relief of itch. In a four-week IV proof-of-concept study in biologic- and JAK-inhibitor-naïve patients with moderate-to-severe atopic dermatitis (AD), all 17 randomized patients were evaluable at the June 8, 2026 cutoff; median follow-up was 71 days. Patients received three 450 mg doses. The company reported placebo-adjusted EASI improvement of 35.6% at Week 1, 61.1% at Week 2, 63.5% at Week 4, and 79.0% at Week 6. At Week 6 it reported placebo-adjusted EASI-50 and EASI-75 response proportions of 82% and 64%; among treated patients with available visits, 7/11 achieved EASI-75. Itch improvement reportedly began on Day 1, and TARC and IgE reductions persisted after dosing. Treatment-emergent adverse events occurred in 50% of treated patients versus 60% on placebo; one Grade 3 event considered probably treatment-related resolved within hours. No conjunctivitis was reported. The estimated half-life is approximately 33 days, and reported treatment-emergent antibodies were low-titer, with no apparent neutralizing activity. These encouraging findings are preliminary and based on a very small early-phase study.

BBT001 is also in development for chronic spontaneous urticaria (CSU). The company expects first-half 2027 results from 12-week IV AD studies in biologic-naïve and biologic-experienced patients and a 14-week IV CSU study. The first patient has been dosed in a 12-week SubQ AD proof-of-concept substudy; Phase 2b SubQ AD study start-up is planned by year-end 2026, using an adaptive design and an active standard-of-care biologic control to select a dose for pivotal development. Quarterly maintenance dosing is a development hypothesis supported by preliminary PK and modeling, not an established regimen. Potential expansion into prurigo nodularis, alopecia areata, bullous pemphigoid, and chronic pruritus remains contingent on results.

BBT002 targets IL-4Rα and IL-5 for respiratory and allergic disease. Preliminary healthy-volunteer results indicate an estimated 29-day half-life and dose-dependent biomarker effects, including TARC reduction and eosinophil depletion lasting at least eight weeks. Safety and tolerability endpoints were reported as met; treatment-emergent antibodies were described as low-titer without apparent PK or safety impact. BBT002 is being studied in COPD and chronic rhinosinusitis with nasal polyps (CRSwNP), and a global Phase 2a SubQ asthma study has begun. The company expects four-week COPD and 12-week CRSwNP proof-of-concept results in the first half of 2027 and plans to start a SubQ Phase 2b dose-ranging respiratory study in 2027. Clinical efficacy has not been established.

Earlier pipeline and market positioning

BBT003, a TL1A/IL-23p19 bispecific for ulcerative colitis and Crohn’s disease, remains preclinical; clinical development is planned by the end of 2026. In a mouse colitis model, the company reported a 67% reduction in disease activity index on Day 5, along with improvements in pathology, inflammation, and fibrosis. These animal results do not demonstrate human benefit. BBT004, also preclinical, is designed to deplete pathogenic B cells and antibody-producing plasma cells for autoantibody-driven disease; IND-enabling work is underway, with no human data reported.

The company describes large potential markets across its indications, including estimates of $35 billion for AD and CSU by 2030, nearly $85 billion for BBT002-addressable Type 2 inflammatory diseases, and $39 billion for IBD. Competitor sales—including 2025 Dupixent sales of approximately $17.8 billion—demonstrate commercial demand, but BBTX’s market estimates and proposed advantages are not evidence of future adoption or product differentiation. The company may expand its capabilities in clinical development, manufacturing, regulatory affairs, and commercialization, and may pursue licensing or co-development partnerships.

Execution, financing, and principal risks

As of June 30, 2026, BBTX reported raising $136.1 million in gross proceeds through private financings; this section does not provide revenue, cash balance, cash flow, or other financial results from which to assess runway. Development and potential commercialization will require substantial further resources. The company has paid approximately $4.8 million for the BBT001 and BBT002 programs. Those agreements include annual fees, development milestones of up to approximately $1.8 million per program, commercial milestones of up to $11.0 million per program, and specified platform fees. For BBT003, BBTX paid a $1.0 million upfront license fee and may owe development and commercial milestones, royalties, and separate Adimab payments. These contingent obligations are not all amounts already paid.

Manufacturing is fully outsourced: WuXi Biologics is the sole manufacturer for BBT001–003 and BioNTech Zhuhai for BBT004. BBTX has no manufacturing facilities, making supply continuity, quality, regulatory compliance, and the time required to qualify alternative suppliers material risks. Intellectual-property protection is also developing: as of October 9, 2026, the company reported seven owned and five in-licensed patent families but no issued patents. Applications may not issue or provide meaningful protection; third-party rights could require licenses or changes to development plans.

As of September 30, 2026, BBTX had 30 full-time employees, including 24 in R&D. Its candidates remain subject to clinical, regulatory, manufacturing, and reimbursement uncertainty; trials may be delayed or fail, and approval would require extensive testing and regulatory review. SubQ injector products may face added combination-product requirements. Coverage, pricing pressure, healthcare-policy changes, and competition could limit commercial returns even if products are approved. The company reported no litigation believed likely to have a material adverse effect.

Management, Board and Governance

The section reports no financial results, balance-sheet data, or cash-flow metrics. It describes recent leadership changes and governance arrangements planned for the offering.

Co-founder Shanshan Xu, CEO and President, became board Chair in September 2026, combining the CEO and Chair roles; Howard Liang was appointed lead independent director. Jonathan Lieber joined as CFO in September 2026 and also serves part-time as CFO of Rallybio. Co-founder Thang Ho became Chief Development Officer in March 2026, after serving as Chief Scientific Officer, and Crystal MacKay became COO in July 2026 after finance and business-operations roles. The leadership team’s experience spans biotechnology, clinical development, finance, investment banking, and operations.

The five-member board consists of Xu and four non-employee directors: Derek DiRocco, Christian Foerster, co-founder Helmut Jeggle, and Liang. The company considers all four non-employee directors—80% of the board—independent under Nasdaq standards; Xu is not independent while serving as CEO and Chair. Directors bring biotechnology investment, pharmaceutical and biotech leadership, scientific, finance, and operating experience.

Before completion of the offering, the board is to be divided into three classes with staggered three-year terms: Foerster and Jeggle in Class I (terms expiring 2027), DiRocco in Class II (2028), and Liang and Xu in Class III (2029). The company notes that the classified board could delay or prevent a change in control. CEO–Chair duality is balanced by a lead independent director, though the structure may also slow shareholder-driven board changes.

Following the offering, the audit committee will comprise DiRocco, Foerster, and Liang, with Liang as chair and designated audit committee financial expert. The compensation committee will comprise DiRocco (chair) and Liang; the nominating and corporate governance committee will comprise Foerster (chair) and Jeggle. Committee responsibilities include financial reporting and internal controls, executive and equity-plan compensation, director nominations and succession planning, governance and board evaluation, ethics and conflicts, and compliance with stock-ownership guidelines. Board and committee risk oversight also covers legal and regulatory compliance, compensation risks, credit and liquidity, operations, cybersecurity, information security, and privacy. The compensation committee members have not been company officers or employees, and the filing reports no executive-compensation committee interlocks. Governance guidelines and a code of business conduct and ethics are planned to take effect before the offering; committee charters become effective with the registration statement.

Director Compensation and Protection

Before the offering, the company had no formal non-employee director compensation policy and reimbursed meeting-related expenses. No non-employee director received compensation for board service in FY2025; Xu, the only director who was also an officer, received no additional board compensation.

At December 31, 2025, Jeggle held 1,901,354 unvested shares granted under a May 2024 stock purchase agreement. Former director Sean Marett, who left the board on December 31, 2025, held options for 6,129 shares for director service and options for 245,181 and 55,165 shares for consulting services. These options were granted December 19, 2024, at a $0.34 exercise price and expire December 18, 2034. His consulting agreement runs through September 2026 unless otherwise determined.

Liang began serving as a non-employee director in July 2026. His agreement provides a $35,000 annual cash retainer and an option for 153,908 shares at an $8.04 exercise price, vesting monthly over three years from July 1, 2026. Vested options are exercisable for 12 months after termination, and vesting accelerates fully upon a change in control. Upon an IPO, his annual retainer is expected to rise to $40,000, with an additional $15,000 for audit committee chair service, subject to the director policy.

The policy effective with the offering sets annual cash retainers at $40,000 per non-employee director and $30,000 for the non-executive board chair. Additional annual fees are $20,000/$10,000 for audit committee chairs/members, $15,000/$7,500 for compensation committee chairs/members, and $10,000/$5,000 for nominating and governance committee chairs/members. Committee fees are in addition to the base retainer; committee chairs receive the chair fee rather than the member fee. Fees are paid quarterly in arrears, prorated for service, with no per-meeting payments; reasonable travel expenses are reimbursed.

New non-employee directors receive initial options for 45,000 shares, vesting monthly over three years; annual awards cover 22,500 shares and generally vest after one year or immediately before the next annual meeting, with a new director’s first annual award prorated. Awards are nonstatutory options with a 10-year term and an exercise price equal to grant-date fair market value. Outstanding director awards accelerate fully immediately before a change in control if the director remains in service through the transaction. Beginning with the first fiscal year after the registration statement becomes effective, annual director compensation is capped at $750,000, or $1.0 million in a director’s initial service year, measured using cash retainers plus grant-date GAAP fair value of equity awards, subject to stated exclusions.

Amended and restated charter and bylaws provide director and officer liability limits to the maximum extent permitted by Delaware law, indemnification, and advancement of defense expenses, subject to limited exceptions. Separate indemnification agreements may provide broader coverage and require advancement of reasonably incurred expenses. The company maintains D&O insurance and reported no known pending or threatened proceedings for which director or officer indemnification had been sought.

Executive compensation

In 2025, CEO Shanshan Xu received total compensation of $1,156,022—salary of $458,750, discretionary bonus of $257,508, option-award grant-date fair value of $427,514, and a $12,250 401(k) match. Thang Ho, then Chief Scientific Officer, received $824,540—salary of $337,500, bonus of $150,009, option-award grant-date fair value of $328,719, and an $8,312 match. No stock awards were reported. Option values are ASC 718 grant-date fair values, not cash received or value realized.

During 2025, Xu’s annual base salary increased from $325,000 to $525,000, and Ho’s increased from $275,000 to $375,000. Their target bonuses were 50% and 35% of salary, respectively. Post-offering confirmatory offer letters set Xu’s salary at $672,700 with a 60% target bonus ($403,620) and Ho’s salary at $523,000 with a 40% target ($209,200). Ho was subsequently promoted to Chief Development Officer. Jonathan Lieber began as CFO in September 2026 at $500,000 salary and a 40% target bonus; any 2026 bonus deemed earned is prorated to 50% of target.

Equity awards and severance

August 2025 options covered 167,124 shares for Xu and 128,503 shares for Ho, each at a $1.84 exercise price, with four-year vesting. Ho also received a September 2026 option for 261,079 shares at $13.57; Lieber received a September 2026 option for 440,282 shares at $13.57, also subject to four-year vesting. In connection with the offering, Xu was approved for options covering 379,102 shares at the IPO price and performance-based PSUs for up to 758,204 shares. The PSUs require the stock price to reach twice the IPO price during a 30-day measurement period within the three years beginning April 1, 2027, and continued service; a qualifying change in control can satisfy the price condition. Xu also holds MiNeng common shares, of which 2,593,822 remain subject to a service-based repurchase option. Ho’s earlier option included regulatory milestones that were achieved in 2025. Because common stock was not publicly traded at December 31, 2025, its accounting fair value was $4.81 per share.

The offering-related Severance Plan replaces prior offer-letter severance terms. Outside a change-in-control period, qualifying termination provides Xu 12 months’ salary continuation and COBRA, plus acceleration of time-based awards scheduled to vest over the next 12 months; Ho receives nine months’ salary continuation and COBRA. For qualifying terminations from three months before through 12 months after a change in control, benefits include a lump sum of 1.5 times salary plus target bonus for Xu or one times for Ho, 18 or 12 months of COBRA, respectively, and full acceleration of outstanding equity awards, with performance awards generally deemed achieved at target. Benefits are subject to conditions including a release. Conditional excise-tax gross-ups are capped companywide at 1.0% of change-in-control enterprise value.

Equity and incentive plans

The 2024 Stock Plan had options covering 1,550,428 shares outstanding and no restricted stock awards as of June 30, 2026; its maximum authorization is 4,208,339 shares. It terminates for new grants when the 2026 Plan takes effect, while existing awards remain outstanding under its terms.

The 2026 Equity Incentive Plan initially reserves 5,560,163 shares, plus up to 4,208,339 carried over from the 2024 Plan. Beginning in FY2027, its reserve increases annually for ten years by the lesser of 5% of fully diluted shares outstanding at the prior fiscal year-end or another amount set by the administrator. The sizable rollover and evergreen feature create potential dilution, although the excerpt does not provide enough information to calculate a dilution percentage. The plan permits a broad range of equity awards and gives the administrator discretion over vesting, acceleration, repricing and transaction treatment. Options generally have a ten-year maximum term and an exercise price at least equal to grant-date fair value. In a change in control, awards not continued or assumed generally accelerate in full; outside-director awards receive full acceleration. Director compensation is capped at $750,000 in annual cash and equity grant-date fair value, or $1,000,000 in a director’s first year.

The 2026 ESPP initially reserves 505,469 shares, with annual increases for ten years beginning FY2027 equal to the least of 1,516,407 shares, 1% of fully diluted shares, or another administrator-set amount. Employees may contribute up to 15% of eligible compensation; shares are purchased at no less than 85% of the lower fair market value on the first trading day of the offering period or the exercise date. Offering periods may last up to 27 months. The plan includes qualified and nonqualified components and expires in 2046.

The October 2026 Employee Incentive Compensation Plan allows awards based on a wide range of financial, operational, commercial, R&D, regulatory and individual goals, using GAAP or non-GAAP measures with potential adjustments. The administrator may increase, reduce or eliminate awards or the bonus pool; awards may be paid in cash or equity, and generally require continued employment through payment. The filing provides no award amounts, expense or performance outcomes.

The company reports no material executive perquisites, defined-benefit plans or nonqualified deferred-compensation balances. Its 401(k) match is 100% of contributions up to 1% of eligible compensation plus 50% of contributions above 1% through 6%, vesting over two years. A Dodd-Frank/SEC-compliant incentive-compensation recovery policy became effective in connection with the offering.

Related-party financing and transactions

BBTX’s related-party activity was driven primarily by preferred-stock financings involving directors, executives, and investors holding more than 5% of its stock. The financing amounts below are total proceeds for each round, not amounts purchased solely by related parties.

• Series Seed (June 2024): BBTX issued 5,329,584 shares at $0.9570 per share, raising approximately $5.1M. Related-party purchases included $3.600M from Salvia Investment, affiliated with director Helmut Jeggle; $1.200M from INCE Capital-affiliated entities; $0.200M from RLG, associated with Sean Marett; and $0.100M from CEO Shanshan Xu through MiNeng.
• Series Seed Plus (August 2024): BBTX issued 3,740,038 shares at $2.4064 per share, raising approximately $9.0M. Purchases included $4.000M each from Biotechnology Value Fund-affiliated entities and Dawn Holdco; $0.500M from entities affiliated with Thomas Strüngmann; $0.200M from RLG; and $0.100M from MiNeng.
• Series A-1 (February–April and June 2025): BBTX issued 15,593,907 shares at $5.6997 per share for approximately $88.9M, including a June milestone closing of 6,237,556 shares. Listed related-party purchases totaled approximately $74.880M: RA Capital-affiliated entities, $23.500M; Strüngmann-affiliated entities, $10.000M; Salvia Investment, $9.000M; Biotechnology Value Fund-affiliated entities, Janus Henderson, and Redmile Biopharma, $7.500M each; Dawn Holdco and INCE Capital-affiliated entities, $3.750M each; RLG, $2.280M; and MiNeng, approximately $0.100M. The shares were reclassified as Series A-1 in October 2025 in connection with the Series A-2 sale.
• Series A-2 (October 2025 and January 2026): BBTX issued 2,728,032 shares at $12.1225 per share for approximately $33.1M, including an additional January closing of 82,490 shares. Listed related-party purchases totaled approximately $31.159M. Major purchasers were Strüngmann-affiliated entities, $10.750M; RA Capital-affiliated entities, $4.278M; INCE Capital-affiliated entities, $4.000M; Biotechnology Value Fund-affiliated entities, $3.174M; Redmile Biopharma, $3.000M; and Salvia Investment, $2.250M. Other purchases were Dawn Holdco, $1.805M; Janus Henderson, $1.402M; and RLG, $0.500M.

Separately, in April 2024 Salvia GmbH, controlled by Jeggle, lent BBTX $0.500M at 3% annual interest. BBTX repaid the principal and $2,712 of interest in July 2024. In May 2024, BBTX issued founder common shares at $0.00001 per share: 8,239,199 shares to CEO-affiliated MiNeng for $53.34 and 4,119,600 shares to Jeggle-affiliated Salvia for $26.67. In May 2026, 823,919 MiNeng shares were transferred to the Xu Trust.

Investor rights and governance

Certain investors, including CEO-affiliated entities and the named major investors, have registration rights and are parties to voting and right-of-first-refusal/co-sale agreements. The voting and right-of-first-refusal/co-sale agreements, and the investors’ rights agreement, terminate upon completion of the offering, except that registration rights continue.

Underwriters reserved up to 3.5% of offering shares for directors, officers, employees, business associates, and related persons; purchases through that program would reduce shares available to the general public.

BBTX’s formal related-person transaction policy and audit-committee review procedures become effective only upon completion of the offering. Consequently, the related-party transactions described above occurred before adoption of the policy and were not subject to those procedures, an important historical governance and conflict-of-interest consideration.

Principal stockholders

Beneficial ownership is reported as of October 23, 2026. Pre-offering percentages are based on 40,386,875 shares outstanding, assuming the Preferred Stock Conversion and Liquidity Event RSU Settlement. Post-offering percentages use 49,761,875 shares, assuming no exercise of the underwriters’ option—an increase of 9,375,000 shares, or approximately 23.2%. The table excludes shares holders may purchase in the offering and shares issuable under the reserved share program. Beneficial ownership reflects sole or shared voting or investment power under SEC rules; shares underlying options exercisable within 60 days are included in the applicable holder’s calculation.

Directors and executive officers as a group (seven persons) beneficially own 17,762,864 shares, equal to 43.5% before and 35.4% after the offering. This includes 17,292,096 shares and 470,768 shares underlying options exercisable within 60 days. Xu’s holdings include 221,017 option shares; Thang Ho holds 228,375 option shares; and Howard Liang holds 21,376 option shares. Derek DiRocco and Christian Foerster report no beneficial ownership. Helmut Jeggle is listed with Salvia’s 8,889,301 shares but disclaims beneficial ownership except to the extent of his pecuniary interest. Xu’s holdings are through MiNeng, the Xu Trust, and options.

Ownership is concentrated among several large holders, and directors and executive officers collectively hold a substantial stake. The offering lowers reported ownership percentages without changing the listed holders’ share counts; Dawn is at 5.0% post-offering, while INCE falls below 5%, to 4.5%.

Capitalization upon closing

This section describes capital-stock terms expected to take effect when the offering closes; it does not report operating or earnings results. The company is authorized to issue 1.2 billion shares: 1.0 billion common shares and 200.0 million preferred shares, each with a par value of $0.00001.

Assuming all preferred shares convert and liquidity-event RSUs are settled as if completed on June 30, 2026, the company would have 40.386875 million common shares outstanding. This includes 2.866703 million unvested restricted shares; the assumed conversion adds 27.391561 million shares, and RSU settlement adds 621,192 shares. No preferred shares are expected to remain outstanding after closing. Under this assumed capitalization, there were 28 holders of record.

As of June 30, 2026, options under the 2024 Plan covered 1.550428 million common shares, with a $0.90 weighted-average exercise price.

Common-stock rights and potential resale supply

Common holders are entitled to one vote per share. Dividends are discretionary, subject to legal availability and any priority rights of preferred stock. Common stock has no preemptive, conversion, redemption, or sinking-fund rights.

Holders of up to 39.750360 million shares—nearly all common shares in the assumed post-conversion capitalization—will have registration rights, potentially creating future resale supply, subject to contractual restrictions and underwriter cutbacks. Demand Form S-1 rights begin 180 days after the registration statement’s effective date; holders of at least a majority of registrable shares may request one registration covering at least 40% of those shares. Form S-3 rights permit up to two registrations in any 12-month period, subject to a minimum anticipated offering price of $5 million, net of specified selling expenses. The company may defer a qualifying registration once in any 12-month period for up to 120 days under specified conditions. Piggyback rights also apply to most company registrations.

The company bears specified registration expenses, but not underwriting discounts, selling commissions, or transfer taxes; reimbursement for one holder-selected counsel is capped at $30,000 per registration. Registration rights generally end for a holder when it owns less than 1% of registrable shares and can sell all of them without Rule 144 limits within a three-month period, upon certain liquidation events, or five years after the offering closes.

Preferred-stock authority and governance provisions

The board may issue authorized preferred stock in series without another stockholder vote and determine each series’ dividend, voting, conversion, redemption, and liquidation rights. Depending on those terms, preferred issuance could dilute common voting power, reduce common holders’ prospects for dividends or liquidation proceeds, or impede a change in control.

Several provisions may entrench the board or delay or deter takeovers: a three-year staggered board; removal of directors only for cause while the board is classified; no cumulative voting or stockholder action by written consent; limited stockholder authority to call special meetings; board control over director vacancies and board size; and a two-thirds voting threshold for stockholder amendments to specified governing-document provisions.

Delaware’s Section 203 generally restricts business combinations with an interested stockholder owning 15% or more for three years, subject to exceptions that include specified prior board approval, 85% ownership upon completion of the transaction, or board approval followed by a two-thirds vote of disinterested outstanding voting stock.

The bylaws designate Delaware courts for most internal-affairs claims and federal courts for Securities Act or Exchange Act claims, subject to stated exceptions. The company has applied to list its common stock on the Nasdaq Global Select Market under “BBTX”; listing is not represented as completed.

Shares Eligible for Future Sale

Based on shares outstanding as of June 30, 2026, and assuming the preferred stock conversion and settlement of liquidity-event RSUs, BBTX expects 49,761,875 common shares outstanding after the offering, including 2,866,703 unvested restricted shares.

The IPO will sell 9,375,000 shares, approximately 18.8% of post-offering shares. These shares are generally freely tradable once sold, except for shares purchased by affiliates or through the reserved-share program by directors, officers, and employees. The remaining shares are restricted securities and generally become eligible for public sale, subject to applicable resale rules and lock-ups, 181 days after the prospectus date. At that point, 32,568,026 shares will be held by affiliates and subject to Rule 144 restrictions, excluding affiliate shares acquired through the reserved-share program.

The company, its directors and officers, and substantially all equity holders have agreed not to sell or otherwise transfer shares for 180 days, subject to exceptions and possible underwriter consent. Certain employees may establish Rule 10b5-1 trading plans, but sales under those plans cannot begin before the lock-up expires. After the lock-up, affiliate sales under Rule 144 are generally capped in any three-month period at the greater of 1% of shares outstanding—approximately 497,619 shares immediately after the offering—or the average weekly trading volume during the preceding four calendar weeks; other Rule 144 requirements also apply.

Holders of up to 39,750,360 shares have registration rights. If a registration statement covering those shares becomes effective, they could become freely tradable, subject to affiliate restrictions, potentially increasing the supply of shares available to the market. BBTX also intends to file a Form S-8 promptly after the offering to register shares underlying existing and future equity awards. Registered shares may become eligible for sale upon filing, subject to vesting, affiliate restrictions, lock-ups, and market-standoff provisions.

Because BBTX had no prior public trading market, the effect of these increases in available shares on the share price is uncertain. The post-lock-up release, registration of equity awards, and possible registered sales by holders with registration rights create a meaningful supply overhang that could pressure the share price and impair the company’s ability to raise equity in the future.

Material U.S. Federal Income Tax Considerations for Non-U.S. Holders

This discussion describes general U.S. federal income tax considerations for non-U.S. holders acquiring the company’s common stock in the offering; it is not individualized tax advice. It is based on laws and guidance that may change, potentially retroactively, and the company has not requested an IRS ruling. The discussion does not address state, local, or non-U.S. taxes, gift or estate taxes, the Medicare contribution tax, or many investors subject to special tax rules.

Dividends

The company has never declared or paid cash dividends and does not expect to do so after the offering. If it makes a distribution, the portion up to current or accumulated earnings and profits generally is treated as a dividend. Any excess generally is a return of capital, up to the holder’s tax basis, and then capital gain.

Dividends paid to non-U.S. holders generally are subject to 30% U.S. withholding tax on the gross amount. A lower treaty rate may apply if the holder provides appropriate IRS Form W-8 documentation. Dividends effectively connected with a U.S. trade or business generally are not subject to this withholding if the holder provides appropriate certification, but are taxed at applicable U.S. rates. A foreign corporate holder may also be subject to a 30% branch profits tax, potentially reduced by treaty.

Sale or Other Disposition of Shares

Non-U.S. holders generally are not subject to U.S. federal income tax on gains from selling or otherwise disposing of shares, except when gains are effectively connected with a U.S. trade or business; certain individual holders are present in the United States for at least 183 days during the relevant calendar year and meet other conditions; or the shares are treated as an interest in a U.S. real property holding corporation (USRPHC).

The company believes it is not, and will not become, a USRPHC, but cannot assure this. That determination depends on the relative fair market values of its U.S. real property interests and other assets. If the company is a USRPHC, the rule generally applies to regularly traded shares only for holders who owned more than 5% of the shares, directly, indirectly, or constructively, during the applicable holding-period window.

Gains that are effectively connected with a U.S. trade or business generally are taxed at U.S. rates, and a corporate holder may also owe branch profits tax. Certain individuals present in the United States for 183 days or more may be taxed at 30% on gains, subject to treaty relief and possible offsets for qualifying U.S.-source capital losses.

Information Reporting, Backup Withholding, and FATCA

Dividend payments and certain U.S.-related payments of sale proceeds may be subject to information reporting and backup withholding unless the holder properly certifies non-U.S. status. Backup withholding is a tax prepayment, not an additional tax; eligible holders may claim a credit or refund.

FATCA generally imposes 30% withholding on dividends paid to foreign financial institutions that do not satisfy applicable agreement, reporting, or exemption requirements, and to non-financial foreign entities that do not provide required certifications regarding substantial U.S. owners or establish an exemption. Proposed Treasury Regulations eliminate FATCA withholding on gross sale proceeds; taxpayers may rely on those regulations pending final regulations or withdrawal. Different rules may apply under intergovernmental agreements.

Underwriting and offering terms

BBTX agreed to sell 9.375 million common shares in its IPO through a four-underwriter syndicate. The underwriters have a 30-day option to purchase up to 1.40625 million additional shares at the IPO price less the underwriting discount. The excerpt’s offering-price, underwriting-discount, and proceeds table is blank, so gross and net proceeds cannot be determined. BBTX estimated $4.6 million of company-paid offering expenses, excluding underwriting discounts, and agreed to reimburse certain underwriter expenses up to $40,000.

The company, its executives and directors, and substantially all existing security holders are subject to a 180-day lock-up, subject to specified exceptions. BofA Securities and Evercore may release locked-up securities at their discretion. Company exceptions include equity-plan issuances and strategic-transaction issuances capped at 5% of shares outstanding immediately after the offering; recipients generally must agree to lock-up terms. Up to 3.5% of the offered shares are reserved for specified directors, officers, employees, distributors, business associates, and related persons, which could reduce the number available to the public.

Trading and market risks

No public market existed before the offering, and an active market may not develop; the shares could trade below the IPO price. The IPO price will be negotiated based on BBTX’s and the industry’s prospects, financial information, development stage, comparable-company valuations, and market conditions. Underwriters may conduct stabilizing transactions and short covering that could support or maintain the share price; those effects may not reflect the price that would otherwise prevail and may end without notice. Underwriters and affiliates may have other commercial, investment-banking, trading, and research relationships with BBTX, creating potential conflicts.

BBTX expected to list on Nasdaq under ticker BBTX, subject to approval. This section provides no operating results, balance-sheet metrics, or business-performance developments.

Distribution restrictions

The shares are not registered or offered for general public sale in the jurisdictions below. Offers and resales are limited by local securities laws and applicable investor or exemption requirements:

• Australia: Offers are limited to sophisticated, professional, or other exempt investors; purchasers generally may not resell in Australia for 12 months after allotment unless an applicable exemption or compliant disclosure document applies.
• Hong Kong: Offers are limited to professional investors or other circumstances that do not constitute a public offer or prospectus; public-directed offering materials are restricted.
• Japan: Shares are unregistered and may not be offered or sold in Japan or to Japanese persons except in compliance with applicable law.
• Singapore: The prospectus is unregistered with the Monetary Authority of Singapore; offers are restricted to institutional investors, specified relevant persons, or other permitted exemptions. Certain investment-holding corporations or trusts acquiring under section 275 generally face a six-month transfer restriction, subject to exceptions.
• Canada: Purchasers must act as principal and be both accredited investors and permitted clients. Resales must rely on an exemption or otherwise fall outside prospectus requirements. Provincial or territorial misrepresentation remedies may apply within statutory time limits; the underwriters are exempt from NI 33-105 conflict-of-interest disclosure requirements for this offering.
• Korea: Shares are unregistered and offered as a private placement; offers, sales, delivery, and resale are restricted, and purchasers must comply with Korean securities and foreign-exchange requirements.
• Brazil: Shares are not registered with the CVM and may be offered only to Brazilian professional investors through a non-Brazilian account, with settlement outside Brazil in non-Brazilian currency. Trading on regulated Brazilian securities markets is prohibited.
• Israel: Shares are unregistered and not ISA-approved; offers are limited to a small number of persons and specified qualified investors, who must confirm eligibility and acknowledge the restrictions in writing.

Legal Matters

Wilson Sonsini Goodrich & Rosati, P.C. (Boston) is acting as company counsel for the offering and will provide an opinion on the validity of the common shares offered. Latham & Watkins LLP (New York) is addressing certain legal matters for the underwriters. The section reports no financial metrics, business risks, or strategic developments.

Independent Auditor

PricewaterhouseCoopers LLP (PwC), the independent registered public accounting firm, audited the financial statements for the year ended December 31, 2025, and for the period from inception on March 14, 2024 through December 31, 2024. The audit covered the balance sheets as of December 31, 2025 and 2024.

PwC’s report includes an explanatory paragraph regarding the company’s ability to continue as a going concern and refers readers to Note 1. This is a material financial-risk flag; the section summary does not provide further detail on the underlying conditions.

The prospectus forms part of BBTX’s Form S-1 registration statement. Additional information about the company and offering, including filed exhibits, is available in the registration statement and through the SEC. Once the registration statement becomes effective, BBTX will be subject to Exchange Act reporting requirements and expects to make periodic reports and proxy materials available free of charge on its website after filing them with the SEC. This section discloses no financial results, material business developments, or company-specific risks.

Business and operating results

Bambusa Therapeutics is a single-segment, clinical-stage biotechnology company developing bispecific antibodies for immunological and inflammatory disorders. It has no product revenue and evaluates performance using consolidated net loss and program spending. The 2024 comparison covers only March 14, 2024 (inception) through December 31, 2024, so it is not a full-year comparison.

For FY2025, research and development expense was $38.096M, up from $13.025M in the 2024 inception period; general and administrative expense was $5.910M, up from $0.855M. Total operating expenses and operating loss were $44.006M and $(44.006)M, respectively, compared with $13.880M and $(13.880)M. Net loss was $(41.087)M, versus $(13.741)M. Other income, net, was $5.152M, including $3.310M of Australian R&D incentive income and $2.171M of interest income, partly offset by a $0.454M expense from the preferred-stock tranche-right fair-value change. Income tax expense was $2.233M.

FY2025 program and expense detail included external R&D of $15.519M for BBT001 and $12.979M for BBT002, compared with $6.165M and $5.063M, respectively, in the 2024 inception period. Other R&D, R&D personnel, external G&A, G&A personnel, and stock-based compensation were $3.064M, $3.844M, $2.018M, $1.205M, and $5.377M, versus $0.626M, $1.039M, $0.703M, $0.091M, and $0.193M. The segment’s reported measure, consolidated net loss, was $(41.087)M versus $(13.741)M; other segment items were $(2.919)M versus $(0.139)M, comprising interest and incentive income, tranche-right fair-value changes, other income, and income tax.

From February 12–December 31, 2025, net loss attributable to common stockholders was $(39.332)M, basic and diluted loss per share was $(6.08), and weighted-average shares were 6,474,305. No EPS was reported for the 2024 inception period. At December 31, 2025, 33,083,918 potentially dilutive securities were excluded as antidilutive, plus 247,241 option shares excluded because performance conditions were unmet. Share and per-share amounts were adjusted for the 1.54485-for-1 forward split effected October 23, 2026.

Balance sheet, cash flows, and financing

At December 31, 2025, total assets were $95.713M, compared with $9.764M at December 31, 2024; total stockholders’ equity (deficit) was $(49.170)M, compared with $(13.548)M. Goodwill and intangible assets other than goodwill were not separately reported. Cash and cash equivalents were $50.643M, versus $9.362M, and marketable securities were $39.984M, versus none. FY2025 Treasury securities had $39.924M amortized cost and $39.984M fair value, with $0.060M unrealized gains and no unrealized losses; all maturities were within one year. The company reported no credit losses on these securities.

Operating cash flow was $(39.804)M in FY2025, compared with $(4.634)M in the 2024 inception period. Capital expenditures were not separately reported. Investing cash flow was $(39.728)M, principally reflecting $47.228M of marketable-security purchases and $7.500M of maturities. Financing cash flow was $120.813M, including net proceeds of $88.778M from Series A-1 and $32.007M from Series A-2 preferred stock. Common shares outstanding were 12,358,799 at the start of 2025 and 12,374,122 at year-end.

FY2025 preferred financings included gross proceeds of $53.3M and $35.6M from Series A-1 closings, and $32.1M from Series A-2. Total preferred stock at year-end was 27,309,071 shares, with $135.235M carrying value and $135.050M liquidation preference, compared with 9,069,622 shares, $13.996M, and $14.100M at year-end 2024. A contingent A-1 tranche-right liability was initially recorded at $1.817M, increased by $0.454M, and settled at $2.271M when the clinical milestone was achieved and shares issued in June 2025. Preferred holders have liquidation priority and conversion rights, including conversion upon qualifying public offerings. The company also issued 82,490 A-2 shares for approximately $1.0M gross proceeds in January 2026.

Development commitments, dilution, and risk

The company’s licensing and research agreements support its pipeline but create contingent costs. The BioNTech Zhuhai assignment covers BBT001 and BBT002 and includes an Alloy platform sublicense; the company incurred $0.1M of annual/platform fees and $0.5M of development milestones in FY2025, with further development and commercial milestones possible. A separate BioNTech Zhuhai collaboration covered two programs and had $1.0M of aggregate research fees, fully paid by year-end 2025. A September 2025 exclusive worldwide license for BBT003 involved $1.0M of upfront expense, plus potential development, sales, and commercial milestones and low-single-digit royalties. The related Adimab arrangement included a $0.5M paid license fee and further contingent milestones and royalties. In May 2026, BioNTech Zhuhai discontinued its Alloy sublicense, releasing the company from the associated annual platform fee.

Stock-based compensation was $5.377M in FY2025, versus $0.193M in the 2024 inception period. Founders’ share compensation was $5.0M in FY2025; 4,495,176 restricted shares remained unvested at year-end. Outstanding options totaled 1,526,912, and reserved potential share issuance increased to 36,012,586 from 24,518,121, largely due to preferred-stock conversion rights and equity awards. The company also had 870,183 cash-settled value appreciation rights; no expense was recorded because performance conditions were not considered probable.

The company has incurred recurring losses and negative operating cash flows and had an accumulated deficit of $54.8M at year-end 2025. The auditor’s opinion was unqualified but highlighted substantial doubt about the company’s ability to continue as a going concern. As of August 3, 2026, management did not expect cash and marketable securities to fund operations for at least 12 months. It is pursuing an IPO and may seek additional equity or debt financing, alliances, or licensing; availability and terms are uncertain, and failure to raise funds could delay, reduce, or end programs. Key risks also include lengthy development and regulatory pathways and reliance on a limited number of CROs and manufacturers.

FY2025 income tax expense arose primarily from Australian taxable income despite consolidated losses. U.S. federal and state NOL carryforwards were $13.3M and $11.1M; a full valuation allowance offset deferred tax assets of $12.710M, leaving net deferred tax assets at zero. Ownership changes could limit use of NOLs and credits.

Bambusa Therapeutics — financial statements and related disclosures

Business and operating results

Bambusa Therapeutics is a pre-commercial, single-segment biotechnology company developing bispecific antibodies for immunological and inflammatory disorders. It has no product revenue and remains dependent on external capital. Its H1 2026 comparison period is not like-for-like: H1 2025 covers February 12–June 30, 2025, rather than a full six months.

For H1 2026, R&D expense increased 73.6% to $20.646M from $11.892M, while G&A expense declined to $3.413M from $3.556M. Total operating expenses and operating loss were $24.059M from $15.448M. Interest income was $1.313M from $0.732M, and Australian R&D incentive income was $1.513M from $1.236M; total other income was $2.893M from $1.551M. Net loss widened to $22.360M from $14.747M, and comprehensive loss was $22.439M from $14.687M. Net loss attributable to common stockholders was $22.360M, or $2.56 per share, versus $12.989M, or $2.30 per share, in the partial-period 2025 comparison. Weighted-average shares were 8,727,671 from 5,657,176.

The company reports one operating and reportable segment, with resource allocation guided by cash availability and projected operating expenses. H1 external R&D by program was: BBT001, $6.636M from $3.950M; BBT002, $5.073M from $3.097M; and early programs, $5.368M from $0.448M. Other R&D was $0.141M from $0.659M, R&D personnel expense $3.065M from $1.520M, external G&A $2.017M from $0.819M, and G&A personnel expense $1.108M from $0.469M. The sharp increase in early-program spending accompanied substantial growth in the two lead programs. Stock-based compensation was $0.651M from $4.486M; other segment items were $(1.699)M from $(0.701)M, comprising interest income, R&D incentive income, fair-value changes in a preferred-stock tranche-right obligation, other income and tax.

Financial position, cash flow and going concern

At June 30, 2026, total assets were $77.496M, down from $95.713M at December 31, 2025. Cash and cash equivalents were $46.534M from $50.643M; marketable securities were $24.941M from $39.984M; together they totaled $71.475M from $90.627M. The Treasury securities had $24.941M fair value and $24.960M amortized cost, including a $20K unrealized loss; all matured within one year. Stockholders’ deficit was $70.958M from $49.170M, including accumulated deficit of $77.188M from $54.828M. Preferred stock classified as temporary equity had a $136.231M carrying value. Goodwill and other intangible assets were not reported; tangible common equity was a $70.958M deficit.

H1 operating cash use was $20.137M from $19.040M; no capital expenditures were reported. Investing activities provided $15.032M, principally from $30.000M of marketable-security maturities, partly offset by $14.968M of purchases. Financing provided $0.996M in H1 2026, versus $88.794M in H1 2025, which the cash-flow summary attributes to Series A-1 issuance. Cash declined $4.109M in H1 2026, compared with a $69.754M increase in H1 2025.

Management concluded substantial doubt exists about the company’s ability to continue as a going concern: as of September 14, 2026, available cash and marketable securities were not expected to fund operations for at least 12 months from that date. Bambusa expects continued losses and negative cash flows and is pursuing an IPO and potentially other equity or debt financing, credit facilities, alliances or licensing. Funding, its timing and sufficiency are uncertain; failure to obtain it could delay, reduce or terminate development programs or threaten continued operations.

Capital structure, compensation and commitments

In January 2026, Bambusa issued 82,490 Series A-2 preferred shares for approximately $1.0M. At June 30, preferred shares outstanding totaled 27,391,561, with $136.231M carrying value and $136.050M liquidation preference. Preferred shares have priority over common stock and are convertible; automatic IPO conversion requires at least $8.5496 per share, $50M gross proceeds and an approved exchange listing. No dividends had been declared. Separately, the company reported $1.0M of H1 related-party A-2 purchases by certain management, MiNeng and Salvia; the comparable H1 2025 related-party A-1 issuance was 1,596,583 shares for $9.1M.

Common shares outstanding were 12,374,122 at both the start and end of H1 2026 (versus 12,358,799 at both points in the H1 2025 period). At June 30, 2026, 2,866,703 founders’ shares remained subject to repurchase. Options outstanding were 1,550,428, with a $0.90 weighted-average exercise price, 7.91-year remaining term and $11.078M aggregate intrinsic value; $1.3M of service-condition compensation remained unrecognized. Cash-settled value appreciation rights (VARs) totaled 901,429, but none were vested or settled and no expense or liability was recorded because performance conditions were not considered probable. Potentially dilutive securities were excluded from diluted EPS as antidilutive.

The BioNTech Zhuhai arrangements and related licenses create material contingent potential payments, including BBT003 development, commercialization and sales milestones, plus royalties and annual fees. No contingent milestones were accrued because they had not occurred or were not considered probable. Zhuhai did not renew its Alloy license in May 2026, releasing Bambusa from the associated $7,500 annual platform fee per program. Research, clinical and service contracts are generally terminable without significant penalty; there were no material legal proceedings or claims reported.

Subsequent developments

After period-end, the company granted options and VARs in July and September 2026, including options on 1,353,356 shares at $13.57 in September. In October it cancelled liquidity-event VARs and granted 701,797 RSUs subject to performance and service conditions; IPO-related vesting is expected to result in additional compensation expense. The new 2026 equity plan initially reserves 5,560,163 shares, with potential carryover of up to 4,208,339 shares from the 2024 plan. On October 23, 2026, Bambusa effected a 1.54485-for-1 forward stock split, with share and per-share figures adjusted retroactively; the prospectus cover references an offering of 9,375,000 common shares.