BlossomHill Therapeutics, Inc. 424B4final IPO prospectus

Executive Summary

BlossomHill Therapeutics develops small-molecule cancer medicines; it has no approved products or revenue, so its investment case rests on clinical progress rather than commercial growth. Spending is accelerating as trials expand: FY2025 net loss was $(60.6)M, nearly twice FY2024’s loss, and Q1 2026 loss doubled Y/Y to $(21.0)M. The $150M all-primary IPO at $16.00 implies a $490M market capitalization and gives IPO buyers 30.6% ownership before outstanding equity awards. The lead opportunity is BH-30643 for treatment-resistant lung cancer, but preliminary responses must become durable benefits at a tolerable dose; proceeds finance development milestones, not the complete path to commercialization.

The Offering

• Size and implied valuation: 9,375,000 shares at $16.00 raise $150M gross; 30,643,660 post-offering shares imply $490M capitalization and 30.6% ownership for IPO buyers. Revenue and earnings multiples are not meaningful because the company is pre-revenue and loss-making. Including remaining existing options and IPO option grants gives 33,290,686 fully diluted shares, $533M capitalization and 28.2% buyer ownership, without assuming exercise proceeds or future ungranted awards.
• Structure and proceeds: All shares are newly issued; proceeds go to BlossomHill, not selling holders. Net proceeds are ≈$135M after $10.5M underwriting commissions and ≈$4.6M expenses. The 30-day option covers 1,406,250 additional shares; full exercise raises gross proceeds to $173M and net proceeds to ≈$156M.
• Deployment: ≈$70.0M for BH-30643, including a potential registrational Phase 2 trial; ≈$20.0M for BH-30236; ≈$15.0M for BH-501284’s regulatory submission and Phase 1 initiation. Remaining funds support other R&D, capital expenditures and operations; management retains allocation discretion.
• Dilution: Each $16.00 share is backed by $7.91 of net tangible assets after the IPO—a $8.09 gap. Existing holders paid $12.29 per share on average. Future award reserves include 5,280,528 shares under the new equity plan, inclusive of IPO grants, and 302,529 under the employee stock purchase plan; these overlap with some awards already counted above.
• Capitalization bridge: Before the IPO, cash was $116M and equity $(152)M. Preferred conversion and option-related issuance produce pro forma cash of $119M and equity of $107M; the offering then adds ≈$135M net proceeds. “After IPO” below assumes all these events and no underwriter-option exercise.
• Execution: Final prospectus dated 8/6/2026; delivery expected on or about 8/10/2026. Listing: Nasdaq Global Select Market, BLSM. Lead underwriters: J.P. Morgan, Leerink Partners and Guggenheim. The directed program reserves ≈1% for employees, directors, officers, business associates, investors and related individuals.
• Resale overhang: Directors, officers and substantially all shareholders have 180-day lock-ups ending 2/2/2027, subject to exceptions and waivers. Substantially all 21,268,660 non-offering shares are initially restricted; holders of 18,258,960 shares have registration rights, creating substantial potential future sale supply.

Key Financial Highlights

Dollar amounts in $M. Annual periods are audited; interim periods are unaudited. Balance-sheet figures are historical period-end amounts except the explicitly labeled After IPO column.

• Spending driver: FY2025 R&D grew 76.5%; Q1 2026 grew 108%. Lead-program external costs rose to $9.55M from $1.78M in Q1 as enrollment, trial sites and manufacturing expanded.
• Cash-flow relationship: FY2025 cash use was below net loss principally because operating assets and liabilities contributed $10.8M, alongside $2.8M noncash charges—not because the business generated revenue.
• Equity explanation: The pre-IPO deficit reflects $156M accumulated losses and $257M convertible preferred stock held outside common equity. Conversion moves that preferred balance into permanent equity; it does not erase losses. Total liabilities were $38.7M, including $23.0M operating lease liabilities, so the equity deficit is not a measure of borrowing.
• Funding trajectory: FY2025 cash increased through preferred financing, including $83.9M net proceeds. Management projects funding into Q1 2028 after the IPO, but expects further capital requirements before approval and commercialization.

Business Model and Growth Drivers

BlossomHill’s prospective revenue model is commercialization of internally discovered oncology drugs, potentially supported by partnerships. Its wholly owned portfolio avoids current in-license obligations, but commercial capabilities still need building.

• BH-30643: Oral, brain-active inhibitor targeting multiple epidermal growth factor receptor mutations. The initial opportunity is C797S resistance, affecting ≈3,200 U.S. patients annually with no approved oral targeted therapy. Preliminary partial responses were 8/15 patients without prior chemotherapy and 8/19 after chemotherapy; results include unconfirmed responses and median follow-up was only 4.2 months. Management plans regulatory discussions in Q4 2026, potential pivotal Phase 2 initiation in Q1 2027 and durability updates during 2027.
• BH-30236: Phase 1 program targeting abnormal RNA splicing in acute myeloid leukemia and higher-risk myelodysplastic syndromes. The venetoclax-combination group reported 4/11 responses in relapsed/refractory leukemia; updated safety and efficacy data are expected in H1 2027.
• BH-501284: Preclinical inhibitor intended to address multiple KRAS mutations beyond G12C. Management plans an investigational new drug submission in Q1 2027; animal activity does not establish human efficacy.
• Execution model: Clinical work and manufacturing are outsourced. Active pharmaceutical ingredients for both clinical candidates come from China; alternative suppliers are being pursued, but no long-term manufacturing commitments exist.

Governance and Control

• Voting and ownership: Post-IPO common stock has one vote per share. The ownership table projects founders J. Jean Cui and Y. Peter Li and affiliates at 13.0%, Cormorant at 10.8% and OrbiMed at 6.8%; directors and executives collectively hold 33.7%. These percentages use that table’s 30,624,872-share denominator, distinct from offering capitalization.
• Governance protections: Cui and Li are spouses and the only non-independent directors. A staggered board, director removal requiring cause and 66⅔% approval, and restrictions on shareholder action impede changes in control.
• Compensation and reporting: IPO-effective grants cover 1,544,599 options, generally vesting over four years. Annual equity-plan reserve increases can reach 5% of outstanding shares, adding recurring dilution. Emerging-growth-company exemptions include reduced disclosures and no auditor internal-control attestation.

Risk Assessment

• Going concern and refinancing: The auditor highlighted substantial doubt; the IPO extends runway but does not finance the full development-to-commercialization cycle.
• Lead-drug safety and durability: BH-30643’s short follow-up limits efficacy conclusions; treatment-related severe liver-enzyme elevations affected 7.1% of the 196-patient safety dataset, with additional Grade 4 cases after cutoff.
• Regulatory pathway and enrollment: A potential accelerated-approval route requires regulator agreement, adequate mutation-specific enrollment and potentially an approved companion diagnostic.
• Pipeline uncertainty: BH-30236 targets a mechanism whose earlier inhibitors encountered toxicity; BH-501284 remains preclinical, leaving limited validated diversification.
• Manufacturing dependence: China sourcing and lack of long-term supply agreements expose trials to trade restrictions, supplier failures and replacement delays.
• Key personnel: Dependence on scientific founder Cui and other experienced executives makes departures or unavailability a threat to discovery and development execution.
• Commercial differentiation: Established therapies and well-funded competitors require meaningful clinical advantages; small early response datasets do not establish market share or pricing power.

Investor Actionables

At $16.00, buyers must accept that early clinical signals can support a commercially differentiated oncology portfolio worth the implied $490M capitalization. Proceeds primarily buy the trials and evidence needed to test that proposition.

• Lead-program validation: Starting from 53% and 42% preliminary C797S response rates, examine 2027 durability and liver-safety updates. Sustained confirmed responses with manageable toxicity support the case; fading responses or dose limitations weaken it.
• Second-program validation: Starting from 4/11 combination responses, assess the company’s planned H1 2027 update. Reproducible remissions and tolerable dosing support diversification; inconsistent benefit or toxicity undermine it.
• KRAS execution: Track the planned Q1 2027 submission and subsequent Phase 1 initiation. Progress into human testing supports the platform strategy; delays or adverse human findings weaken the preclinical thesis.
• Runway discipline: Compare future cash use and program progress with management’s Q1 2028 funding projection. Reaching planned milestones before refinancing supports execution; earlier financing needs without corresponding progress increase dilution risk.