BBTX Bambusa Therapeutics, Inc. 424B4 final IPO prospectus section summaries

Bambusa Therapeutics, Inc. — IPO cover

Bambusa Therapeutics is offering 10,555,555 common shares at $16.00 per share, for $168.889 million in gross proceeds. Underwriting discounts and commissions are $11.822 million ($1.12 per share), leaving $157.067 million ($14.88 per share) before offering expenses. The underwriters have a 30-day option to purchase up to 1,583,333 additional shares at the IPO price less the underwriting discount. Up to 3.5% of the offered shares may be reserved for persons associated with the company.

There was no public market for the shares before the offering. The shares have been approved for listing on the Nasdaq Global Select Market under ticker BBTX. The prospectus is dated October 29, 2026, and delivery is expected on or about November 2, 2026.

Bambusa identifies as an emerging growth company and a smaller reporting company, and has elected to use certain reduced public-company reporting requirements. The prospectus refers investors to risk factors beginning on page 16.

Bambusa Therapeutics — Prospectus Summary

Business and pipeline

Bambusa Therapeutics is a clinical-stage biopharmaceutical company developing long-acting bispecific antibodies for immunology and inflammation. It describes its candidates as “pipeline-in-a-molecule” programs that may address multiple indications through complementary disease pathways. Its target global I&I market is projected to exceed $200 billion by 2030. As of June 30, 2026, Bambusa had raised $136.1 million in gross proceeds through private financings. It has worldwide rights to its programs, or says it can obtain them on commercially reasonable terms, and relies on third-party antibody engineering, including collaboration with BioNTech Zhuhai.

BBT001 (IL-4Rα/IL-31) is being developed for atopic dermatitis (AD) and other inflammatory skin diseases. In July 2026, Bambusa reported positive topline proof-of-concept results from a four-week intravenous study in bio-naïve patients with moderate-to-severe AD. All 17 enrolled patients were evaluable at the June 8 data cutoff; median follow-up was 71 days after first dose (range 33–165 days). Placebo-adjusted EASI improvement was statistically significant and clinically meaningful from Week 1, deepened through Week 6, and was sustained during follow-up. At Week 6, placebo-adjusted EASI-50 and EASI-75 response rates were 82% and 64%. Itch improvement began on Day 1 and continued for eight weeks after the last dose; TARC and IgE also declined. Preliminary tolerability was favorable, with no conjunctivitis reported; treatment-emergent anti-drug antibodies were low-titer, with no apparent neutralizing activity. The observed half-life, pharmacokinetics, receptor occupancy, and duration of response support the company’s expectation that quarterly maintenance dosing may be possible, but this is not an established regimen.

Bambusa expects first-half 2027 topline readouts from 12-week IV AD studies in bio-naïve and bio-experienced patients, and a 14-week IV chronic spontaneous urticaria (CSU) study. A 12-week SubQ AD substudy has begun dosing; the company plans to start Phase 2b AD dose-ranging activities by year-end 2026, using an adaptive design and an active biologic control to select a dose for pivotal development. BBT001 is also in global and China AD studies and a China CSU study.

BBT002 (IL-4Rα/IL-5) targets respiratory and allergic diseases. Preliminary global Phase 1 healthy-volunteer results showed an estimated half-life of approximately 29 days, rapid and sustained dual biomarker effects—including TARC reduction and eosinophil depletion for more than eight weeks—and favorable safety, tolerability, and low immunogenicity. Bambusa says the findings support potential quarterly maintenance dosing. Studies include global and China COPD trials, a China chronic rhinosinusitis with nasal polyps (CRSwNP) study, and an initiated global SubQ asthma Phase 2a study. First-half 2027 readouts are expected for four-week IV COPD and 12-week IV CRSwNP proof-of-concept studies; a SubQ Phase 2b dose-ranging study in a respiratory indication is planned for 2027.

BBT003, targeting TL1A and IL-23p19 for inflammatory bowel disease, is planned to enter clinical development by year-end 2026. BBT004 is a preclinical dual B-cell depletion candidate for autoantibody-driven autoimmune diseases. The company’s potential indication expansions remain prospective. Its platform architecture originated at BioNTech Zhuhai; Bambusa cites third-party trials of the distinct bispecific pumitamig in more than 2,000 patients as validation of the architecture, not of Bambusa’s candidates.

Financial results

Bambusa has no established product revenue and depends on developing and commercializing its candidates. Amounts below are in millions, except per-share data.

H1 operating expenses increased 55.7% year over year, principally because R&D expense rose 73.6%; G&A declined. H1 other income included interest income of $1.313 million (versus $0.732 million) and R&D incentives of $1.513 million (versus $1.236 million). H1 2025 included a $0.454 million expense from a fair-value change in the preferred-stock tranche-right obligation. FY 2025 other income included $3.310 million of R&D incentives and $2.171 million of interest income. Income tax provision was $1.194 million in H1 2026, $0.850 million in H1 2025, and $2.233 million in FY 2025. The 2024 comparison covers only the period from inception, not a full year.

Liquidity, offering, and capitalization

At June 30, 2026, cash and cash equivalents were $46.534 million, marketable securities $24.941 million, working capital $63.076 million, total assets $77.496 million, total liabilities $12.223 million, convertible preferred stock $136.231 million, and stockholders’ deficit $70.958 million. Pro forma for preferred-stock conversion, liquidity-event RSU settlement, and charter/bylaw changes, stockholders’ equity was $65.273 million. Pro forma as adjusted for the offering, cash and cash equivalents would be $198.967 million, working capital $217.253 million, total assets $228.185 million, liabilities $10.479 million, and stockholders’ equity $217.706 million.

The offering is for 10,555,555 shares at an assumed $16.00 per share, with an underwriters’ option to purchase 1,583,333 additional shares. Estimated net proceeds are $152.4 million, or $176.0 million if the option is exercised in full. Planned uses include approximately $90 million for BBT001 (including the planned Phase 2b AD study), approximately $40 million for BBT002 (including a planned respiratory Phase 2b trial), and the remainder for other R&D, BBT003 and BBT004, capital expenditures, working capital, and public-company costs.

Immediately after the offering, 50,942,430 shares are expected outstanding, or 52,525,763 with full exercise of the option. The base count includes conversion of preferred stock into 27,391,561 common shares and settlement of 621,192 liquidity-event RSUs (potentially up to 701,797). Excluded are 1,550,428 options outstanding at June 30, 2026 (weighted-average exercise price $0.90), 1,621,449 later-granted options (weighted-average exercise price $12.66), 379,102 IPO options, 758,204 IPO performance-based RSUs, and outstanding value appreciation rights. The 2026 equity plan reserves 5,898,951 shares, including IPO options and performance-based RSUs; the ESPP reserves 505,469 shares. Both plans provide for automatic annual increases. Share figures reflect a 1.54485-for-1 forward split effected October 23, 2026. A reserved-share program makes 3.5% of the offered shares available to specified insiders and associates, and some purchases may not be subject to lock-up restrictions.

A preliminary, unaudited September 30, 2026 estimate put cash, cash equivalents, and marketable securities at approximately $57.2 million. Management said this would not fund operations for at least 12 months from when the financial statements become available to be issued and disclosed substantial doubt about the company’s ability to continue as a going concern. The estimate had not been audited, reviewed, or otherwise assured. Management expects significant losses and negative cash flows for the foreseeable future; additional capital will be needed even if the IPO succeeds, potentially diluting shareholders, constraining operations, or requiring the company to relinquish rights.

Principal risks and reporting status

Development is costly, lengthy, and uncertain: early or interim findings may not predict later results, and regulators may require additional studies or delay approvals. Extended half-life could prolong adverse events, and biologic-device combinations may add approval complexity. Even approved products could face safety issues, weak adoption, unfavorable pricing or reimbursement, healthcare reforms, or a smaller-than-expected market. Bambusa depends on third parties for research, trials, and manufacturing, including sole-source suppliers; delays, noncompliance, or relationship failures could disrupt development. Other risks include competition, hiring and scaling, intellectual-property protection, collaborations and licenses, macroeconomic and geopolitical conditions including U.S.-China relations, and out-licensing that could reduce the pipeline. The company has material weaknesses in internal control over financial reporting and warns that failure to remediate them could affect timely or accurate reporting. Its stock may be volatile.

Bambusa is an emerging growth company and smaller reporting company, uses reduced disclosure, and has elected the extended transition period for new accounting standards.

Risk factors

Development, regulatory and commercial uncertainty

BBTX is a clinical-stage biotechnology company with no approved products and no product-sales or royalty revenue. BBT001 and BBT002 are in early clinical development; BBT003 and BBT004 remain preclinical. The company has limited operating history, has never completed a pivotal trial or commercialized a product, and expects commercialization—if achieved—to be many years away. It expects three candidates in clinical development by the end of 2026.

Development is lengthy, costly and uncertain. Candidates may fail because of safety or efficacy results, trial design or execution, enrollment and retention, manufacturing readiness, or regulatory requirements. Promising early findings may not translate to later trials or other indications; preliminary results may change after verification. No serious adverse events had been observed in BBT001 and BBT002 studies as of the stated data cutoffs, but larger or longer studies could reveal new safety issues. Delays can increase costs, postpone or prevent approval, and allow competitors to reach the market first. Foreign trial data may not be accepted by regulators, and injectable candidates may face additional review as biologic-device combination products.

No candidate has been approved in any jurisdiction. Regulators may require additional studies, reject data or endpoints, impose narrow labels or post-marketing obligations, or delay reviews. Fast Track or Breakthrough Therapy designations are uncertain and do not assure approval or faster review; BBTX sought Fast Track designation for one candidate but did not receive it. Even approval may not produce profitable sales: adoption depends on clinical differentiation, physician and patient acceptance, pricing, reimbursement, supply, distribution and competition. Market-size estimates may overstate eligible demand, and some target populations may be too small to support profitability.

BBTX competes in crowded inflammation and immunology markets against companies with greater financial, technical, manufacturing and commercial resources. Competitors may develop better, safer or cheaper treatments, obtain approval sooner, secure stronger reimbursement, or limit BBTX’s access to trial participants, sites, employees and technologies.

Losses, liquidity and financing

BBTX has funded operations primarily through preferred-stock financing and has negative operating cash flows. It expects substantial losses and increasing R&D and commercialization-related spending, and may never become profitable. Management concluded there is 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.

From inception through June 30, 2026, the company received $136.1 million from issuing convertible preferred stock. At June 30, 2026, it had $71.5 million of cash, cash equivalents and marketable securities. Assuming the offering closes and current plans hold, the offering proceeds and existing resources are expected to fund operations into late 2028; estimates depend on uncertain development and trial assumptions, and funds will not carry all candidates through regulatory approval. Further financing will be needed. If unavailable on acceptable terms, BBTX may have to delay, reduce, suspend or abandon programs. Equity or convertible financing would dilute holders; debt could impose security interests or restrictive covenants; collaborations could require surrendering valuable rights. Insolvency of a bank holding company funds could also impair access to cash.

Execution, suppliers, partnerships and contractual obligations

BBTX relies on CROs, investigators, clinical sites and third-party manufacturers, with limited control over their performance, compliance, capacity or quality. Many suppliers are sole-source; a WuXi Biologics subsidiary performs most IND-enabling CMC work for some candidates. Failure, disruption or termination could interrupt supply, require technology transfer or repeated studies, increase costs, or delay trials and approval. BBTX remains responsible for regulatory compliance when work is outsourced.

Reliance on China-based providers, including WuXi Biologics, BioNTech Zhuhai and Tigermed, exposes development and supply to political, regulatory, trade, currency and IP risks. Tariffs, export restrictions and U.S.–China measures could raise costs or disrupt materials, data and manufacturing; replacement suppliers could be difficult to secure. The BIOSECURE Act and related restrictions may affect federal funding and partners’ views of Chinese suppliers; the DOJ Data Security Program restricts certain data transfers involving countries of concern, and proposed COINS Act rules could further constrain China-related biotechnology activity.

Collaborators may underfund, delay, discontinue or redirect programs, pursue competing products, or fail to commercialize candidates. BBTX could lose funding, milestones, royalties or development rights, and may be unable to find replacement partners. Under the BioNTech Zhuhai agreements, contingent obligations include up to $1.8 million in development milestones and $11.0 million in commercial milestones per program under the Assignment Agreement; the License Agreement includes up to $6.9 million in development milestones, $57.5 million in first-commercial-sale milestones and $217.5 million in sales milestones, plus low-single-digit royalties on licensed-product net sales. These obligations could weigh on future results.

Intellectual property, regulation and data

The patent portfolio is early-stage: BBTX owns or in-licenses no issued patents, and it expects most patents from current applications will not issue for at least four years. Pending applications may fail to issue or provide enforceable protection; third-party claims or blocking patents could require costly licenses, redesigns, damages or abandonment of programs. Patent, trade-secret, trademark and ownership disputes could consume cash and management attention, impair partnerships or prevent commercialization. In-licensed rights also depend on licensors’ compliance and may be limited, disputed or terminated.

If approved, products would remain subject to extensive manufacturing, safety, labeling, promotion and post-marketing requirements. Noncompliance or adverse events could lead to clinical holds, recalls, restricted distribution, fines, or withdrawal. Reimbursement and pricing controls—including U.S. and foreign government policies, Medicare negotiation and potential most-favored-nation initiatives—could limit market access, prices and returns on R&D investment.

Cyberattacks, vendor breaches or privacy-law violations could expose sensitive clinical, financial and proprietary data, interrupt trials, or create recovery, litigation and regulatory costs. Privacy obligations are expanding across U.S. states and foreign jurisdictions; GDPR penalties can reach the greater of €20.0 million or 4% of annual worldwide turnover in the EU, and £17.5 million or 4% in the UK. BBTX also faces product-liability, employee and vendor misconduct, anti-corruption, export-control, hazardous-material and business-continuity risks.

Offering, ownership and reporting controls

After the offering, existing holders may sell substantial shares when lock-ups expire; potential sales could pressure the stock and impair future equity fundraising. Directors, officers and holders of at least 5% are expected to control approximately 64.3% of voting stock after the offering, giving them significant influence. Future equity-plan reserves and automatic annual increases could further dilute shareholders. The stock may be volatile, and there is no assurance of an active market; BBTX has never paid cash dividends.

The 2025 audit identified material weaknesses in financial-reporting controls, including insufficient accounting expertise, ineffective journal-entry and reconciliation controls, inadequate segregation of duties, and deficient IT controls. Remediation is underway, but will require investment and may not succeed; further weaknesses could emerge. Inaccurate or delayed reporting could cause restatements, regulatory action, delisting or reduced access to capital. As of December 31, 2025, BBTX had $13.3 million of federal and $11.1 million of state NOL carryforwards; ownership changes could limit their use.

Forward-Looking Statements and Key Uncertainties

The company cautions that estimates, projections, and other forward-looking statements may differ materially from actual outcomes, and that new risks may emerge. These statements speak only as of the prospectus date and generally will not be updated, except as required by law.

Key uncertainties include the safety and efficacy of clinical-trial candidates; trial enrollment, timing, and results; regulatory submissions and approvals; and the market size, acceptance, pricing, and reimbursement of any approved products. The company also identifies risks to its ability to compete and to commercialize, manufacture, and market candidates if approved.

Execution depends in part on third parties for clinical trials and manufacturing. Other company-specific risks include preserving intellectual-property rights and meeting development and commercial milestones under the BioNTech Zhuhai license; securing favorable collaborations, licensing, or out-licensing arrangements; attracting and retaining personnel; and obtaining additional financing, including whether existing cash and short-term investments will cover operating and capital needs. The prospectus also identifies remediation of material weaknesses in internal control over financial reporting and the use of offering proceeds as forward-looking matters.

Industry and Market Information

The prospectus’s industry and market-size information is based on third-party sources, industry publications and reports, as well as the company’s internal data. The company has not independently verified the third-party information, and its internal data has not been verified by a third party. Estimates depend on assumptions and are subject to limitations; uncertainty and risk in the industry could cause actual market conditions to differ materially from those estimates.

Use of IPO Proceeds

Based on an initial public offering price of $16.00 per share, estimated net proceeds are approximately $152.4 million, or $176.0 million if the underwriters exercise their option in full. These estimates are after underwriting discounts and commissions and estimated offering expenses. The company expects the proceeds to strengthen its capitalization and financial flexibility, fund product development, and cover costs associated with operating as a public company.

The company may also allocate some proceeds to future licenses, acquisitions, or investments in complementary businesses, products, or technologies, although it had no specific agreements or commitments for these uses.

Management estimates that IPO proceeds, together with existing cash, cash equivalents, and short-term investments, will fund operating expenses and capital expenditures into late 2028. This estimate relies on assumptions that may prove incorrect: spending could accelerate and require the company to raise capital sooner. Available resources will not fund all candidates through regulatory approval, so substantial additional capital will be needed.

Management has broad discretion in deploying the proceeds. Actual spending will depend on clinical results, trial and regulatory timelines, collaboration funding, and unforeseen cash requirements. Until the proceeds are used, the company expects to hold them in short-term, interest-bearing investment-grade instruments, including AAA-rated money market funds, certificates of deposit, and U.S. government obligations.

The company has never declared or paid cash dividends and does not expect to do so in the foreseeable future. It intends to retain available funds and future earnings to support operations and finance business growth. Any future dividend decision would be at the board’s discretion and would depend on operating results, financial condition, contractual restrictions, and capital requirements. Future debt or preferred securities could further restrict the company’s ability to pay dividends.

Capitalization and IPO

As of June 30, 2026, cash, cash equivalents and marketable securities were $71.475 million on both actual and pro forma bases. The IPO adds approximately $152.433 million after estimated offering costs, bringing the pro forma as-adjusted balance to $223.908 million. The offering comprises 10,555,555 shares at $16.00 per share, net of underwriting discounts, commissions and estimated offering expenses.

Pro forma capitalization assumes conversion of all 27,391,561 preferred shares, carried at $136.231 million, into common stock and settlement of 621,192 liquidity-event RSUs. No preferred shares remain after conversion.

The pro forma share count includes 2,866,703 unvested restricted common shares.

Potential dilution and equity plans

The capitalization share counts exclude the following potential dilution:

• 1,550,428 options outstanding at June 30, 2026, with a $0.90 weighted-average exercise price.
• 1,621,449 options granted after June 30, 2026, with a $12.66 weighted-average exercise price.
• 379,102 IPO options with an exercise price equal to the $16.00 IPO price.
• 758,204 IPO performance-based RSUs.

The 2026 Plan reserves 5,898,951 shares for future issuance, including the IPO options and IPO performance-based RSUs and 338,788 shares carried over from the 2024 Plan. The ESPP reserves 505,469 shares. Both plans provide for automatic annual increases in their share reserves; the 2026 Plan may also receive shares from certain 2024 Plan awards that expire, are forfeited or are repurchased. Additional securities or consideration may be issuable upon settlement of outstanding VARs; the amount is unspecified.

Net tangible book value and IPO dilution

As of June 30, 2026, historical net tangible book deficit was $72.7 million, or $(5.88) per share. After giving effect to conversion of preferred stock into 27,391,561 common shares and settlement of 621,192 Liquidity Event RSUs, pro forma net tangible book value was $63.5 million, or $1.57 per share. These calculations use 40,386,875 common shares, including 2,866,703 unvested restricted shares.

The company is offering 10,555,555 shares at $16.00 per share. After underwriting discounts, commissions and estimated offering expenses, pro forma as-adjusted net tangible book value would be $217.7 million, or $4.27 per share. This represents a $2.70 per-share increase for existing stockholders and $11.73 per-share immediate dilution for new investors.

Post-offering shares and consideration at the $16.00 IPO price

If the underwriters exercise their 1,583,333-share option in full, post-offering ownership would be 77% for existing holders and 23% for offering investors.

Potential additional dilution

The net tangible book value and dilution calculations exclude potential dilution from 1,550,428 outstanding options with a $0.90 weighted-average exercise price; 1,621,449 options granted after June 30, 2026 with a $12.66 weighted-average exercise price; 379,102 IPO Options at the $16.00 IPO price; and 758,204 IPO PSUs.

The 2026 Plan reserves 5,898,951 shares, including the IPO Options and IPO PSUs and 338,788 shares transferred from the 2024 Plan. The ESPP reserves an additional 505,469 shares. Securities or other consideration issuable upon settlement of outstanding VARs are also excluded. The 2026 Plan and ESPP provide for annual automatic increases in their share reserves. The company may also raise capital through equity or convertible debt—even if it believes existing funds are sufficient—which could result in further dilution.

Business, pipeline and outlook

BBTX is a clinical-stage biopharmaceutical company developing long-acting bispecific antibodies for immunology and inflammation (I&I), intended to combine validated pathways and offer durable, convenient subcutaneous treatment. It cites a global I&I market projected to exceed $200B by 2030. Its lead programs are BBT001 (IL-4Rα/IL-31) and BBT002 (IL-4Rα/IL-5); it is also developing BBT003 (TL1A/IL-23p19) and BBT004, with plans to advance BBT003 into clinical development.

BBTX has generated no revenue since its inception on March 14, 2024, and does not expect meaningful product revenue until candidates are successfully developed, approved and commercialized. It expects losses and expenses to increase substantially as programs advance into larger and later-stage trials; development costs, timelines and approval prospects remain uncertain.

Results of operations

$ millions

H1 2026 R&D increased 73.6% year over year, principally from clinical development of BBT001 and BBT002 as they progressed through Phase 1b/2a, and $4.8M of higher BBT003 manufacturing-development costs. Lower stock-based compensation partly offset higher personnel costs. G&A declined modestly: lower professional and external costs, including reduced stock-based compensation, were partly offset by legal and other costs associated with becoming a public company and increased personnel costs. FY 2025 comparisons are against the shorter period from inception through year-end 2024.

H1 R&D expense detail ($ millions)

Liquidity and cash flows

At June 30, 2026, cash, cash equivalents and marketable securities totaled $71.5M, and accumulated deficit was $77.2M. Management said those resources alone would not fund operations for at least 12 months from the financial statements’ issuance; the filing identifies substantial doubt about BBTX’s ability to continue as a going concern. The FY 2025 auditor’s report also included an explanatory paragraph. Separately, management estimated that existing resources plus estimated net offering proceeds would fund operations and capital requirements into late 2028; that estimate depends on assumptions that may prove incorrect.

Cash flows ($ millions)

H1 2026 investing cash provided reflected $30.0M of marketable-security maturities less $15.0M of purchases. Financing primarily reflected preferred-stock issuance: $1.0M net in H1 2026, versus $88.8M net in H1 2025. Since inception, BBTX has raised $136.1M gross from preferred-stock sales. Additional capital will be needed; equity financing could dilute shareholders, debt could impose restrictive terms, and collaborations could require giving up rights. Insufficient funding could delay, reduce or end programs.

Collaborations, obligations and other risks

BioNTech Zhuhai agreements provided access to BBT001, BBT002 and discovery options for up to 10 target combinations through April 12, 2027. BBTX exercised an option for BBT003 and gave notice exercising one for BBT004. Under the BBT003 license, BBTX faces development milestones to obtain an IND by October 9, 2027 and dose a first Phase 2 patient by October 9, 2029, each with a 12-month extension right. Failure to meet obligations or termination could result in loss or reversion of rights and transfer of program materials. Potential payments include BioNTech development and commercial milestones and royalties; BBTX also paid a $1.0M BBT003 upfront fee and owes a $57,500 annual fee until first commercial sale. BioNTech Zhuhai’s May 2026 nonrenewal of its upstream Alloy license eliminated the associated $7,500-per-program annual platform fee. A separate Adimab agreement carries potential milestones and low-single-digit royalties.

Cash-settled value appreciation rights (VARs) had $5.6M intrinsic value at June 30, 2026, up from $2.7M at year-end 2025, but were not recorded because the performance condition was not considered probable. In October 2026, BBTX cancelled 701,797 liquidity-event VARs and granted RSUs covering up to the same number of shares; at the $16.00 IPO price, an estimated 621,192 shares may vest, with $10.0M grant-date fair value. Private-company common-stock valuations rose from $2.41 per share in February 2025 to $13.57 in September 2026, largely reflecting increased modeled IPO likelihood. BBTX identified material weaknesses in internal control over financial reporting relating to 2025 and the inception-to-2024 period; failure to remediate could affect reporting accuracy or timeliness.

Business overview and strategy

BBTX is a clinical-stage biopharmaceutical company developing long-acting bispecific antibodies for immunology and inflammation (I&I). Its strategy is to combine complementary, clinically or commercially validated targets in one molecule, with high-concentration subcutaneous (SubQ) formulations and longer dosing intervals intended to improve disease control and convenience. These advantages remain hypotheses to be established in clinical trials. The company cites an I&I market expected to exceed $200 billion by 2030.

Lead candidates and evidence

BBT001 combines blockade of IL-4/IL-13 signaling with targeting of IL-31-related itch. In its randomized, placebo-controlled four-week IV PoC substudy, 17 bio-naïve adults with moderate-to-severe AD received BBT001 or placebo. Placebo-adjusted EASI improvement was 35.6% at Week 1 and 79.0% at Week 6; at Week 6, 82% achieved EASI-50 and 64% achieved EASI-75. Itch improvement began as early as Day 1, and itch and biomarker reductions were reported to persist for eight weeks after the last dose. The estimated human half-life is approximately 33 days. The company reported favorable tolerability, no conjunctivitis and low-titer anti-drug antibodies without apparent neutralizing activity. These are preliminary results from a very small study, not confirmation of efficacy or safety in larger trials. Quarterly maintenance dosing is a potential, not an established regimen.

Further BBT001 readouts include 12-week IV AD studies in bio-naïve and bio-experienced patients, a 14-week IV CSU study, and a 12-week SubQ AD PoC study. A planned adaptive Phase 2b SubQ AD trial is expected to include an approved biologic as an active control to help select a dose. Potential future indications—including prurigo nodularis, alopecia areata, bullous pemphigoid and chronic pruritus—depend on clinical results.

BBT002 has an estimated human half-life of approximately 29 days. Preliminary healthy-volunteer studies reported sustained pharmacodynamic effects, including TARC reduction and eosinophil depletion, and favorable safety and tolerability; they do not demonstrate patient efficacy. COPD, CRSwNP and asthma studies are at different early clinical stages, with the H1 2027 PoC results important milestones. COPD biologic opportunity depends on identifying and treating an appropriate Type 2/eosinophilic patient population.

BBT003 is supported by preclinical binding and animal-model findings, including a reported 67% reduction in disease activity index on Day 5 in a mouse colitis model. BBT004 is intended to deplete pathogenic B cells and antibody-producing plasma cells. Neither program has established human safety or efficacy.

Markets, financing and execution

The company estimates BBT001’s initial AD/CSU opportunity at more than $35 billion by 2030, and broader dermatology potential above $45 billion. It estimates a 2030 respiratory biologics market above $60 billion and a broader BBT002-addressable Type 2 market approaching $85 billion; its IBD market estimate is $39 billion by 2030. These are company market estimates, not BBTX revenue. Commercial success depends on demonstrating meaningful differentiation from established therapies and achieving adoption, coverage and reimbursement.

BBTX reports $136.1 million in gross proceeds from private financings through June 30, 2026. It plans to build clinical, manufacturing, quality, regulatory and commercial capabilities and may seek partnerships to access expertise, markets and capital. As of September 30, 2026, it had 30 full-time employees, including 24 in R&D.

Agreements, manufacturing and principal risks

BioNTech Zhuhai agreements underpin the pipeline but include contingent costs and rights conditions. For BBT001 and BBT002, BBTX had paid approximately $4.8 million by June 30, 2026; additional pass-through milestones may reach $1.8 million per program for development and $11.0 million per program commercially. The BBT003 license includes a $1.0 million upfront payment, up to $6.9 million in development milestones, $57.5 million in first-commercial-sale milestones and $217.5 million in sales milestones, plus low-single-digit royalties. Development obligations include obtaining an IND approval by October 9, 2027 and dosing a first Phase 2 patient by October 9, 2029, each with a 12-month extension right. Termination under specified conditions could result in rights and materials reverting to BioNTech Zhuhai.

BBTX owns no manufacturing facilities: WuXi Biologics is the sole manufacturer for BBT001–003 and BioNTech Zhuhai for BBT004. Supplier disruption, qualification of replacements, clinical-trial execution, competition, and the company’s ability to fund development are material risks. As of October 9, 2026, it reported seven owned and five licensed patent families, but no issued patents.

All candidates remain investigational. Trials, regulatory review and approval are uncertain; expedited pathways do not guarantee approval. Post-approval requirements, SubQ device regulation, pricing policy, payer coverage and reimbursement could constrain commercialization and returns. The company also faces evolving healthcare, privacy and international regulatory requirements.

Leadership and board

As of October 26, 2026, co-founder Shanshan Xu is CEO, President and Board Chair; she became Chair in September 2026. Jonathan Lieber became CFO in September 2026 and continues part-time as CFO of Rallybio. Co-founder Thang Ho became Chief Development Officer in March 2026, after serving as Chief Scientific Officer from October 2025. Crystal MacKay became COO in July 2026 following finance and business-operations roles at Bambusa.

The five-member board consists of Xu and four non-employee directors—Derek DiRocco, Christian Foerster, Helmut Jeggle and Howard Liang—all identified as Nasdaq-independent. Because Xu is both CEO and Chair, Liang serves as lead independent director. The board’s experience is concentrated in biotechnology, drug development, healthcare finance and life-sciences investing; Xu and Ho have BioNTech experience, and several directors have outside business, investment or board affiliations.

In connection with the offering, the company will adopt a classified board with staggered three-year terms: Foerster and Jeggle are Class I (terms expire 2027), DiRocco is Class II (2028), and Liang and Xu are Class III (2029). The company notes that staggered terms could delay or prevent a change in control.

Governance and oversight

The board will have audit, compensation, and nominating and corporate governance committees. The audit committee comprises DiRocco, Foerster and Liang, with Liang as chair and audit committee financial expert. Its responsibilities include financial reporting and internal controls, auditor oversight, related-party transactions, compliance, and cybersecurity, information-security and privacy risks. The board and committees also oversee liquidity, credit, operational, compensation and governance risks.

After the offering, the compensation and nominating/governance committees will be independent. The compensation committee will oversee executive and director compensation, benefit and equity plans, and clawback policies. The nominating/governance committee will oversee board composition, succession planning, governance, director evaluations, ethics compliance and stock-ownership guidelines. The company adopted a code of business conduct and ethics and corporate governance guidelines before the offering. It reports no known pending or threatened proceedings for which indemnification has been sought.

Director compensation and equity

The company had no formal non-employee director compensation policy before the offering. 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. As of December 31, 2025, Jeggle held 1,901,354 unvested shares.

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. All were granted December 19, 2024, at a $0.34 exercise price and expire December 18, 2034. His consulting agreement continues through September 2026 unless otherwise determined.

The following outside-director compensation policy will take effect in connection with the offering:

Committee retainers are additional to the director retainer; a committee chair does not receive both chair and member retainers for the same committee. Fees are paid quarterly in arrears, with no per-meeting fees.

New non-employee directors will receive an initial option for 45,000 shares, vesting monthly over three years. Eligible directors will also receive annual options for 22,500 shares, generally vesting after one year or immediately before the next annual meeting if earlier; the first annual award for a newly appointed director is prorated. Options have a 10-year term, an exercise price equal to grant-date fair market value, and at least a 12-month post-termination exercise period for vested options. Outstanding director equity awards fully accelerate upon a change in control if the director remains in service through the transaction. Annual cash and equity compensation is capped at $750,000 per non-employee director, or $1 million in the initial service year; equity is valued at grant-date fair value under GAAP.

Liang began non-employee director service in July 2026 under an agreement providing a $35,000 annual 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 the option fully accelerates upon a change in control. In connection with the offering, his retainer is expected to increase to $40,000, with an additional $15,000 annually for audit committee chair service, subject to the outside-director policy.

Indemnification

The amended certificate and bylaws, effective around the offering, limit director and officer monetary liability to the fullest extent permitted by Delaware law, provide indemnification, and require advancement of defense expenses subject to limited exceptions. Separate agreements provide broad indemnification and expense advances, and the company maintains directors’ and officers’ insurance. These arrangements could result in costs if claims arise.

Executive compensation

2025 named executive officer compensation

The 2025 named executive officers were CEO Shanshan Xu and Thang Ho, then Chief Scientific Officer and later Chief Development Officer. Option-award values are ASC 718 grant-date fair values, not cash paid or realized; neither executive received stock awards in the 2025 compensation table.

Xu’s base salary increased from $325,000 to $468,000 in February 2025, $510,000 in June, and $525,000 in October. Ho’s increased from $275,000 to $350,000 in February and $375,000 in September following his promotion. Their 2025 target bonuses were 50% and 35% of base salary, respectively; both received discretionary bonuses. The stated 2026 bonus targets remained unchanged.

Post-IPO confirmatory offer letters specified annual salaries and target bonuses of $672,700 and 60% ($403,620) for Xu, and $523,000 and 40% ($209,200) for Ho. The filing also reports subsequent 2026 salary levels of $542,063 for Xu, and $430,000 in February and $450,000 in April for Ho following promotion.

Equity awards and potential dilution

August 2025 options covered 167,124 shares for Xu and 128,503 for Ho, at a $1.84 exercise price, vesting over four years with a one-year cliff followed by monthly vesting. At December 31, 2025, Xu held 2,593,822 restricted shares through MiNeng, valued at $12.476284M using the company’s $4.81-per-share fair value; the shares remained subject to repurchase and service-based release.

Ho also held the 128,503 options granted in 2025 at $1.84. Portions of his earlier options vested upon first-in-human trial approvals, achieved January 31 and May 6, 2025.

Offering-related awards add further potential dilution. Xu received options for 379,102 shares at the IPO price, vesting over four years, and performance-based restricted stock units for up to 758,204 shares. The units vest only if the stock reaches twice the IPO price over a 30-day period within the three-year performance period beginning April 1, 2027, and Xu remains in service; otherwise they are forfeited. Ho received a September 2026 option for 261,079 shares at $13.57, vesting over four years.

Jonathan Lieber, who joined as CFO on September 15, 2026, has a $500,000 annual salary and 40% target bonus; any 2026 bonus is prorated to 50% of target. His September 2026 option grant covers 440,282 shares at $13.57, vesting over four years from his start date. His confirmatory letter provides benefits similar to Ho’s under the Severance Plan.

Severance, benefits and compensation policies

The post-IPO Severance Plan replaces prior offer-letter severance. For qualifying termination outside a change-in-control period, Xu is eligible for 12 months of salary continuation and COBRA and up to 12 months of time-based equity acceleration; Ho is eligible for nine months of salary continuation and COBRA. For qualifying termination within three months before or 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; COBRA for 18 or 12 months, respectively; and 100% equity acceleration, with performance awards deemed achieved at target. A potential excise-tax gross-up is subject to conditions and a collective cap of 1.0% of transaction enterprise value for executives with similar benefits.

The company provides standard health and welfare benefits and a 401(k) match: 100% of employee contributions up to 1% of eligible compensation, plus 50% of contributions above 1% through 6%; matching contributions vest over two years. Executives generally receive no material perquisites, and the company reports no defined-benefit or nonqualified deferred-compensation plans for them. An offering-related Dodd-Frank/SEC-compliant recovery policy covers incentive compensation following specified restatements caused by material financial-reporting noncompliance. The company has no specific policy on equity-award timing relative to material nonpublic disclosures.

Equity and incentive plans

The 2024 Stock Plan was terminated when the 2026 Plan became effective; existing awards remain outstanding under the 2024 Plan, with no further grants. As of June 30, 2026, 1,550,428 options were outstanding and no restricted stock awards were outstanding; the plan’s maximum authorization was 4,208,339 shares. Options generally have terms up to 10 years, and in a corporate transaction awards may be continued, assumed, substituted, cashed out, or cancelled, including for no consideration.

The 2026 Stock Plan, approved in October 2026, initially reserves 5,560,163 shares, plus up to 4,208,339 carried over from the 2024 Plan or returned under specified circumstances. Beginning in fiscal 2027, its reserve increases annually for 10 years by the lesser of 5% of prior-year-end fully diluted shares or a lower administrator-set amount. The plan authorizes options, restricted stock and units, stock appreciation rights, performance awards and other awards, creating potential dilution. If a successor does not continue an award in a change in control, it accelerates in full; performance awards generally vest at target unless the agreement provides otherwise. The administrator has broad discretion over awards, including vesting, acceleration and repricing. Outside-director annual cash and equity compensation is capped at $750,000 in grant-date GAAP value, or $1 million in the director’s first fiscal year.

The 2026 Employee Stock Purchase Plan initially reserves 505,469 shares, with annual increases beginning in fiscal 2027 equal to the least of 1,516,407 shares, 1% of prior-year-end fully diluted shares, or an administrator-set lower amount. No offering or purchase period had begun. Eligible participants may contribute up to 15% of compensation, and the purchase price is at least 85% of the lower fair market value at the start or end of the offering period; periods may not exceed 27 months. The plan includes qualified and nonqualified components and generally limits annual purchase rights to $25,000. It terminates in 2046 unless ended earlier.

The October 2026 Employee Incentive Compensation Plan permits flexible financial, operational, commercial, research, regulatory or individual goals, with results potentially adjusted for unusual items. The administrator may increase, reduce or eliminate awards; awards are generally cash lump sums but may be settled in equity. Continued employment through payment is generally required, and earned-bonus rights cannot be impaired by plan amendment or termination without participant consent.

Related-party financings and transactions

From June 2024 through January 2026, the company raised approximately $136.1 million through four preferred-stock financings. Directors, the CEO, and holders of more than 5% of the company’s capital stock participated substantially.

Disclosed related-party purchases across the four rounds totaled approximately $119.9 million. Significant investments included:

• Series A-1: RA Capital affiliates invested $23.5 million; Thomas Strüngmann-affiliated entities, $10.0 million; Salvia Investment, $9.0 million; and Biotechnology Value Fund, Janus Henderson, and Redmile Biopharma, $7.5 million each.
• Series A-2: Strüngmann-affiliated entities invested $10.75 million; RA Capital affiliates, $4.28 million; INCE Capital affiliates, $4.00 million; and Biotechnology Value Fund, $3.17 million.
• Earlier rounds: Salvia invested $3.6 million and INCE $1.2 million in Seed; Seed Plus included $4.0 million each from Biotechnology Value Fund affiliates and Dawn Holdco.
• An entity affiliated with the CEO invested approximately $100,000 in each of the Seed, Seed Plus, and Series A-1 rounds.

In May 2024, the company issued 8,239,199 common shares to CEO Shanshan Xu’s entity, MiNeng, and 4,119,600 shares to director Helmut Jeggle’s Salvia Investment, each at $0.00001 per share. The aggregate purchase prices were $53.34 and $26.67, respectively.

In April 2024, Salvia GmbH, controlled by director Jeggle, loaned the company $500,000 at 3% annual interest. The company repaid the principal and $2,712 of interest in July 2024.

Investor arrangements and governance

Certain major investors—including CEO-affiliated entities and the named investment funds—have registration rights under an investors’ rights agreement. Upon completion of the offering, that agreement and the voting agreement terminate, except for the registration rights; the right of first refusal and co-sale agreement also terminates.

A reserved-share program makes up to 3.5% of the shares offered available at the IPO price to directors, officers, employees, business associates, and related persons. Shares purchased through the program would reduce the shares available to the general public.

A written related-person transaction policy takes effect upon completion of the offering. Under the policy, the audit committee reviews covered transactions and approves or disapproves them. The transactions described above occurred before adoption of the policy and were not subject to its review and approval procedures, presenting a governance and potential conflict-of-interest consideration for investors.

Ownership before and after the offering

As of October 23, 2026, the ownership table assumes conversion of preferred stock and settlement of Liquidity Event RSUs. It uses 40,386,875 common shares outstanding before the offering and 50,942,430 after it, assuming the underwriters’ option is not exercised—an increase of 10,555,555 shares, or approximately 26.1%. The table excludes identified holders’ potential offering purchases and shares they might purchase through the reserved share program. For each holder, the ownership calculation includes options exercisable within 60 days; those options are not included in the share-count calculation for other holders.

The listed holders’ share counts are unchanged in the post-offering presentation; their ownership percentages decline as the share base expands. Dawn Holdco and INCE Capital-affiliated entities fall below 5% after the offering. The table reflects concentrated pre-offering ownership among the founder and several institutional or affiliated holders.

Beneficial ownership details

Xu’s 8,623,812 shares comprise 7,562,518 held by MiNeng, 840,277 held by the Xu Trust, and 221,017 shares subject to options exercisable within 60 days. Salvia’s holdings are attributed to its managing director, Helmut Jeggle, who disclaims beneficial ownership except to the extent of his pecuniary interest. The filing similarly notes that certain investment managers, general partners, and affiliated persons may be deemed to share voting or investment power over institutional holdings, while disclaiming beneficial ownership except for pecuniary interests.

The group total includes Xu and consists of 17,292,096 shares plus 470,768 shares subject to options exercisable within 60 days. Other listed individuals include Thang Ho, with 228,375 option shares; Howard Liang, with 21,376 option shares; and Derek DiRocco and Christian Foerster, with no shares reported.

Capital stock and potential dilution

At the offering closing, the company will have authority to issue 1.2 billion shares: 1.0 billion common shares and 200 million preferred shares, each with a par value of $0.00001 per share. Assuming conversion of all preferred shares and settlement of Liquidity Event RSUs as if completed on June 30, 2026, the capitalization would be:

The common shares were held by 28 holders of record. Separately, options outstanding under the 2024 Plan covered 1.550428 million common shares, at a weighted-average exercise price of $0.90 per share.

The board may issue authorized preferred shares in one or more series without another stockholder vote. Preferred-stock terms could give holders rights senior to common stock, potentially diluting common voting power or affecting common-stock dividends and liquidation proceeds.

Registration rights

Investors’ rights holders and their transferees may have registration rights covering up to 39.750360 million common shares. Demand-registration rights begin 180 days after the registration statement’s effective date. Holders of a majority of the registrable shares may request one Form S-1 registration, covering at least 40% of the then-registrable shares. Form S-3 rights allow up to two registrations in any 12-month period, subject to a minimum anticipated public offering price of $5 million, net of specified selling expenses. Holders also have piggyback rights, subject to underwriter and marketing limitations.

The company may defer a qualifying registration request for up to 120 days, but no more than once in any 12-month period. The company generally pays registration expenses, while selling holders bear underwriting discounts, selling commissions and transfer taxes. The company’s reimbursement for one counsel representing the holders is capped at $30,000 per registration. Registration rights generally end for a holder that falls below the specified ownership threshold and can sell under Rule 144, immediately before certain liquidation events, or five years after the offering closes.

Voting, governance and takeover provisions

Each common share carries one vote, with no cumulative voting. The board is divided into three classes with staggered three-year terms, so only one class is elected each year. While the board is classified, directors may be removed only for cause, and vacancies are generally filled by sitting directors. Stockholders cannot act by written consent; special meetings may be called only by the board, its chair, or the CEO or president. Certain charter and bylaw amendments require approval by at least two-thirds of the outstanding voting power. Together with the board’s authority to issue preferred stock, these provisions may delay or deter a change in control.

Delaware General Corporation Law Section 203 generally restricts business combinations with an interested stockholder owning 15% or more for three years, subject to specified exceptions, including prior board approval or required ownership and approval thresholds. The bylaws designate Delaware courts for specified internal-affairs and related claims and federal district courts for Securities Act and Exchange Act claims, subject to stated exceptions.

Other common-stock terms and listing

Common-stock dividends are discretionary and subject to any preferred-stock preferences. Common shares have no preemptive, conversion, redemption or sinking-fund rights. The shares are approved for listing on the Nasdaq Global Select Market under ticker BBTX.

Shares Eligible for Future Sale

Following the IPO, based on shares outstanding as of June 30, 2026 and giving effect to the Preferred Stock Conversion and Liquidity Event RSU Settlement, BBTX expects 50,942,430 common shares outstanding, including 2,866,703 unvested restricted shares.

Most shares other than the IPO shares remain restricted until applicable resale conditions are satisfied. The company, its directors and officers, and substantially all equity holders are generally subject to a 180-day lock-up, unless the underwriters consent to a transfer. After the lock-up expires, restricted shares may become eligible for public sale, subject to applicable securities-law requirements and affiliate restrictions.

Affiliate sales under Rule 144 are generally limited during any three-month period to the greater of 1% of shares outstanding—approximately 509,424 shares immediately after the offering—or the average weekly trading volume during the preceding four calendar weeks, and are subject to other conditions. Rule 701 sales generally cannot begin until 90 days after the prospectus effective date.

The potential supply overhang is also affected by registration rights: effectiveness of a resale registration statement could make up to 39,750,360 shares freely tradable, except for shares held by affiliates, which remain subject to applicable restrictions. A Form S-8 registers shares subject to outstanding options and shares reserved for future issuance under equity plans; any sales remain subject to vesting, lock-up and market-standoff provisions, as well as applicable affiliate limits.

Because no public market existed before the offering, the effect of these newly eligible shares is uncertain. Actual sales—or investors’ expectation that substantial sales may occur when restrictions lapse—could pressure BBTX’s stock price and impair its ability to raise equity capital.

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

This discussion describes certain U.S. federal income tax consequences for non-U.S. holders who acquire the company’s common stock in the offering. It is not comprehensive and does not address state, local, non-U.S., gift, estate, or other specialized tax matters. It is based on tax authorities that may change or be interpreted differently, possibly retroactively. The company has not requested an IRS ruling; investors with particular circumstances should consult their own tax advisers.

Dividends and distributions

The company has never paid cash dividends and does not expect to do so after the offering. If it makes distributions, amounts up to current or accumulated earnings and profits generally are treated as dividends and subject to 30% U.S. withholding tax, unless a lower treaty rate applies and the holder provides appropriate Form W-8 documentation. Distributions exceeding earnings and profits generally first reduce the holder’s tax basis; any remaining excess is treated as capital gain.

Dividends effectively connected with a non-U.S. holder’s U.S. trade or business generally are not subject to the 30% withholding tax, but are taxed at U.S. income-tax rates. A corporate holder may also be subject to branch-profits tax of up to 30%.

Gain on disposition of stock

Non-U.S. holders generally are not subject to U.S. federal income tax on gains from selling the stock, except where the gain is effectively connected with a U.S. trade or business, an individual holder is present in the United States for at least 183 days in the relevant calendar year (subject to applicable conditions), or the stock is treated as a U.S. real property interest.

The company believes it is not, and will not become, a U.S. real property holding corporation (USRPHC), but gives no assurance because that determination depends on the relative fair values of its assets. If the stock is regularly traded, the USRPHC rules generally apply to a holder only if the holder owns more than 5% of the stock, directly, indirectly, or constructively, during the relevant holding period.

Withholding and reporting

Payments connected with the United States may be subject to backup withholding unless the holder properly certifies non-U.S. status. Backup withholding is creditable against any tax owed and is not an additional tax.

FATCA generally imposes 30% withholding on dividends paid to noncompliant foreign financial institutions and certain non-financial foreign entities. Proposed regulations eliminate FATCA withholding on gross proceeds from stock dispositions for as long as those regulations remain applicable; withholding on dividends remains.

IPO offering and underwriting

BBTX agreed to sell 10,555,555 common shares at $16.00 per share in its IPO. Underwriters have a 30-day option to purchase up to 1,583,333 additional shares.

Estimated offering expenses are $4.6 million, excluding underwriting discounts and commissions. BBTX also agreed to reimburse certain underwriter expenses up to $40,000.

BofA Securities, Evercore, UBS and Cantor Fitzgerald are the underwriters. Their purchase commitments are several, not joint; subject to the underwriting agreement and its default provisions, they have agreed to purchase all offered shares if any are purchased.

Trading, lock-up and allocation

The IPO is expected to establish BBTX’s first public market for its common stock. The shares were approved for Nasdaq listing under ticker BBTX, but an active trading market may not develop, and the stock could trade below the $16.00 offering price. Underwriters may use stabilization and short-covering transactions that could support or maintain the share price, but are not obligated to do so and may stop at any time.

BBTX, its executive officers and directors, and substantially all existing security holders are subject to a 180-day lock-up on sales and other transfers, with customary exceptions. During the lock-up, the company may issue securities for specified strategic transactions, capped at 5% of post-offering shares outstanding, provided recipients agree to lock-up terms. BofA Securities and Evercore may release lock-up restrictions at their discretion.

Up to 3.5% of offered shares were reserved for directors, officers, employees and other associated persons; purchases from that allocation reduce the shares available to the general public.

Jurisdictional offering and resale restrictions

The prospectus restricts who may purchase shares and how they may subsequently be transferred in several jurisdictions:

• Australia: Offers are limited to sophisticated or professional investors and other eligible exemptions. Exempt investors generally may not resell in Australia for 12 months after allotment, unless an exemption applies or compliant disclosure is used.
• Hong Kong: Offers are restricted to professional investors or transactions that do not constitute a public offer or prospectus.
• Japan: Shares are unregistered and generally may not be offered or sold in Japan, to Japanese residents, or for their benefit, except as permitted by applicable law.
• Singapore: Offers are limited to institutional investors, specified relevant persons or other exemptions under the SFA. Certain investment-holding corporations and trusts acquiring shares under Section 275 face a six-month transfer restriction, subject to exceptions.
• Canada: Purchasers generally must be accredited investors and permitted clients; resales require an applicable exemption or a transaction outside prospectus requirements. The prospectus also notes an underwriter exemption from specified NI 33-105 conflict-of-interest disclosure requirements for this offering.
• Korea: Shares are unregistered and offered privately; offers, sales and resales are restricted except as permitted by Korean securities and foreign-exchange laws.
• Brazil: Shares are unregistered and may be offered only to professional investors. They must be acquired through a non-Brazilian account and settled outside Brazil in non-Brazilian currency; trading on regulated Brazilian securities markets is prohibited.
• Israel: Shares are unregistered and may not be offered publicly without an ISA-approved prospectus; distribution is limited to a specified number of persons and qualified investors.

Wilson Sonsini Goodrich & Rosati, Professional Corporation (Boston) will provide an opinion on the validity of the common shares offered by the prospectus. Latham & Watkins LLP (New York) will advise the underwriters on certain legal matters related to the offering. The section discloses no specific legal risks or other material developments.

Independent Auditor and Going-Concern Disclosure

PwC LLP, the independent registered public accounting firm, audited BBTX’s 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 also covered the balance sheets as of December 31, 2025 and 2024.

PwC’s audit report includes an explanatory paragraph expressing substantial concern about the Company’s ability to continue as a going concern, as described in Note 1.

BBTX filed an S-1 registration statement for its common-stock offering. Once the registration statement became effective, the company became subject to the reporting requirements of the Securities Exchange Act and said it would file periodic reports, proxy statements, and other required information with the SEC. BBTX stated that these materials would be available free of charge on its website as soon as reasonably practicable after filing. Website content was not incorporated by reference into the prospectus. This section disclosed no financial or operating metrics, performance changes, or business risks.

Business and operating results

Bambusa Therapeutics is a clinical-stage biopharmaceutical company developing bispecific antibodies for immunological and inflammatory disorders. It has one reportable segment, no product-sales revenue, and depends on external financing while funding research and development. The 2024 comparison period runs from the company’s March 14, 2024 inception through December 31, 2024, so it is not a full-year comparison.

FY2025 other income included $2.171M of interest income and $3.310M of Australian R&D incentive income, partly offset by a $0.454M fair-value expense on the preferred-stock tranche-right obligation and a $2.233M income-tax provision. Comprehensive loss was $41.027M, including $0.060M of unrealized gains on marketable securities.

The CEO manages the business on a consolidated basis, with program-level spending and cash resources among the measures considered. External R&D expense was concentrated in BBT001 and BBT002:

Balance sheet, cash flows, and financing

At year-end 2025, the Treasury securities were available-for-sale, with $39.924M amortized cost, a $0.060M unrealized gain, and $39.984M fair value; all matured within one year. The company also held $36.779M of Level 1 money-market funds. Cash and marketable securities together totaled $90.6M.

Investing cash flow was $(39.728)M, primarily from $47.228M of marketable-security purchases, partly offset by $7.500M of maturities. Financing provided $120.813M, principally through Series A-1 and A-2 preferred-stock issuances. Cash increased $41.281M during 2025. Common shares outstanding increased from 12,358,799 at the start of 2025 to 12,374,122 at year-end.

The company raised approximately $121.0M gross in 2025: Series A-1 proceeds were $53.3M in February and $35.6M in June after a clinical milestone was achieved; Series A-2 raised approximately $32.1M in October. In January 2026, it issued a further 82,490 Series A-2 shares for approximately $1.0M. At December 31, 2025, 27,309,071 preferred shares had a $135.235M carrying value and $135.050M liquidation preference. Preferred holders rank ahead of common shareholders in a liquidation. Automatic conversion in a qualifying public offering requires a share price of at least $8.5496, gross proceeds of at least $50M, and an exchange listing.

Liquidity, dilution, and risks

The auditor’s opinion was unmodified but highlighted substantial doubt about the company’s ability to continue as a going concern. As of August 3, 2026, management expected available cash and marketable securities to be insufficient for at least 12 months from that date. The company expects recurring losses and negative operating cash flows to continue and is pursuing an IPO and other potential funding, including equity or debt financings, credit facilities, alliances, and licensing. Funding on acceptable terms is not assured; shortfalls could delay, reduce, or terminate R&D programs or threaten operations.

Stock-based compensation was $5.377M in FY2025, versus $0.193M in the 2024 inception period, including $5.0M of founder-share compensation. At year-end, 4,495,176 founder shares remained subject to repurchase. There were 1,526,912 options outstanding, with $6.076M aggregate intrinsic value, and 870,183 cash-settled value appreciation rights (VARs), with $2.682M aggregate intrinsic value. No VAR expense was recorded because performance conditions were not considered probable; the awards could create a cash obligation if conditions and a liquidity event occur. Shares reserved for preferred conversion, awards, and future plan grants totaled 36,012,586. For February 12–December 31, 2025, basic and diluted loss per share was $6.08, based on a $39.332M loss attributable to common stockholders and 6,474,305 weighted-average shares; 33,083,918 antidilutive securities were excluded.

Development commitments and other matters

Licenses and research agreements provide access to external antibody programs and platform IP but include contingent payments. The BioNTech Zhuhai assignment supports BBT001 and BBT002; FY2025 costs included $0.1M of annual fees and $0.5M of development milestones, with potential development milestones of approximately $1.8M per program and commercial milestones of up to $11.0M per program. A separate research-and-option agreement covered two programs, with $1.0M of aggregate fees. For BBT003, the company paid a $1.0M upfront license fee and may owe development, sales, and commercial milestones, low-single-digit royalties, and an annual $57,500 fee until first commercial sale. A related Adimab agreement included a $0.5M fee and potential milestones and royalties. In May 2026, BioNTech Zhuhai discontinued the Alloy sublicense, releasing the company from the associated annual platform fee.

FY2025 income-tax expense was $2.233M, primarily reflecting Australian taxable income under a transfer-pricing arrangement; U.S. losses generated no tax benefit because of a full valuation allowance. Gross deferred tax assets were $12.710M and fully valuation-allowanced at year-end. Federal and state NOL carryforwards were $13.3M and $11.1M, respectively; use may be limited by ownership-change rules, and the company had not completed a Section 382 analysis.

The company relies on a limited number of manufacturers and research organizations, and faces development, regulatory, competition, intellectual-property, and personnel risks. No material legal proceedings were reported. On October 23, 2026, it effected a 1.54485-for-1 forward stock split; share and per-share amounts were retroactively adjusted, while preferred-stock conversion ratios were unchanged.

Bambusa (BBTX) — Financial statements summary

Operating results

Bambusa is a clinical-stage therapeutics company developing bispecific antibodies for immunological and inflammatory disorders. It has generated no product revenue; results and cash needs are driven by research and development, and commercialization depends on successful development and regulatory approval. The company has one operating and reportable segment.

R&D expense increased 73.6%, reflecting higher program and personnel spending. Other income included $1.313 million of interest income (from $0.732 million) and $1.513 million of Australian R&D incentives (from $1.236 million). Stock-based compensation declined to $0.651 million from $4.486 million, including $0.4 million of Founders’ Shares expense versus $4.4 million. The 2025 per-share and weighted-average-share comparison covers February 12–June 30 only, because common stock was not outstanding for accounting purposes before February 12, 2025.

Segment spending

The company’s chief operating decision-maker manages the business on a consolidated basis. The following program and functional expense detail explains the principal changes in its single segment.

Balance sheet and liquidity

Cash, cash equivalents and marketable securities totaled $71.475 million at June 30, 2026. Treasury securities had $24.960 million amortized cost and a $0.019 million net unrealized loss, versus $39.924 million amortized cost and a $0.060 million unrealized gain at year-end; all maturities were within one year. Accrued expenses and other current liabilities rose to $10.609 million from $7.743 million, notably as accrued legal and professional fees increased to $2.398 million from $0.170 million. Deferred costs for an in-process equity financing were $1.744 million; they would reduce equity proceeds if the financing closes or be expensed if abandoned.

Cash flows and financing

H1 2026 investing cash flow included $30.000 million of Treasury maturities and $14.968 million of purchases. Financing included $0.996 million from Series A-2 preferred issuance, compared with $88.794 million from Series A-1 issuance in H1 2025. Common shares outstanding were 12,374,122 at both the start and end of H1 2026 and 12,358,799 at both the start and end of H1 2025. Related parties purchased $1.0 million of Series A-2 shares in H1 2026, compared with $9.1 million of Series A-1 shares in the 2025 comparison period.

Funding outlook, dilution and development commitments

As of September 14, 2026, management concluded that cash and marketable securities were insufficient to fund operations for at least 12 months from issuance of the financial statements, raising substantial doubt about the company’s ability to continue as a going concern. Bambusa expects continued losses and negative cash flows and is pursuing an IPO and other possible financing, alliances or licensing; availability, timing and acceptable terms are uncertain. Without funding, it may need to delay, reduce or terminate R&D programs. A qualifying underwritten public offering—at least $8.5496 per share, at least $50 million gross proceeds, and an exchange listing—would automatically convert preferred stock. At June 30, preferred stock comprised 27,391,561 shares with $136.231 million carrying value and $136.050 million liquidation preference; preferred holders have liquidation priority over common stock.

Potential dilution is substantial: 34,466,603 shares were reserved for preferred conversion, options, unvested restricted stock and future option grants at June 30, down from 36,012,586 at year-end. Separately, 31,563,511 potentially dilutive securities were excluded from diluted EPS as antidilutive. Options outstanding were 1,550,428, with $11.078 million aggregate intrinsic value; 2,866,703 Founders’ Shares remained subject to repurchase. After quarter-end, the company granted additional options and VARs, and in October granted 701,797 performance- and service-conditioned RSUs, with significant vesting expected to depend on IPO-related share-price performance.

Pipeline economics include the BBT001/BBT002 assignment, initially paid at $4.0 million, with potential development milestones of up to approximately $1.8 million per program and commercial and sales milestones of up to $11.0 million per program. A 2025 exclusive worldwide BBT003 license included a $1.0 million upfront payment, potential development milestones up to $6.9 million, first-sale milestones of $57.5 million and sales milestones of $217.5 million, plus low-single-digit royalties. The company also has Adimab milestone and royalty obligations. No contingent milestones were accrued because they had not occurred or were not considered probable. Research and manufacturing depend on a limited number of CROs and CMOs, creating potential interruption risk. There were no material legal proceedings or claims.

On October 23, 2026, the company effected a 1.54485-for-1 forward stock split; share and per-share figures were retroactively adjusted. The prospectus cover identifies an offering of 10,555,555 common shares.

¹ The 2025 per-share and weighted-average-share period is February 12–June 30 and is not directly comparable with the six months ended June 30, 2026.
² Includes interest income, R&D incentive income, change in fair value of the preferred-stock tranche-right obligation, other income and income tax provision.