Sutro Biopharma, Inc. — 2023 Form 10-K Summary
Reporting period: Fiscal year ended December 31, 2023. This is an annual report; the filing does not provide a clear standalone fourth-quarter income statement. Amounts below are in U.S. dollars unless noted.
Business context
Sutro is a clinical-stage oncology company with no products approved for commercial sale. Its pipeline is built on its cell-free protein synthesis and site-specific conjugation platforms, XpressCF and XpressCF+. Its lead candidate, luveltamab tazevibulin (luvelta), is an ADC targeting folate receptor-alpha, primarily being developed for platinum-resistant ovarian cancer. Other programs include preclinical ADC candidates STRO-003 and STRO-004.
Financial results and liquidity
| Metric | 2023 | 2022 |
|---|---|---|
| Revenue | $153.7 million | $67.8 million |
| Research and development expense | $180.4 million | $137.2 million |
| General and administrative expense | $62.6 million | $59.5 million |
| Loss from operations | $(89.3) million | $(128.9) million |
| Net loss | $(106.8) million | $(119.2) million |
| Net loss per share, basic and diluted | $(1.78) | $(2.35) |
| Cash used in operating activities | $(111.6) million | Cash provided: $3.5 million |
Revenue rose 127%, chiefly due to $97.5 million recognized from Vaxcyte’s exercise of expanded rights under their agreement. Sutro also recognized $34.0 million from Astellas, compared with $10.9 million in 2022. These collaboration and option-related revenues are not product sales and may not recur at the same level. R&D expense increased 32%, largely reflecting manufacturing, outside services, personnel and clinical development costs. The smaller net loss reflected higher revenue and interest income, partly offset by increased expenses, an $18.2 million income tax provision and $12.6 million of non-cash interest expense related to the royalty transaction.
At year-end, cash and cash equivalents were $69.3 million and marketable securities were $264.4 million, totaling $333.7 million. Sutro also held Vaxcyte equity valued at $41.9 million. Current assets were $421.5 million versus current liabilities of $93.7 million. The company reported $4.1 million of debt at year-end; the loan matured March 1, 2024, and the filing states the final payment was made on that date. The separate deferred royalty obligation was $149.1 million at year-end.
Financing included a $140 million upfront payment from Blackstone for specified future Vaxcyte royalties, with up to $250 million in additional payments tied to return thresholds. Sutro accounted for the proceeds as a deferred royalty obligation; it recorded $12.6 million in non-cash interest expense in 2023 using a 17% effective rate. The company also raised approximately $12.0 million net through at-the-market stock sales, issuing 1.86 million shares.
Material changes and operating developments
- Revenue increased substantially, while operating losses narrowed; operating cash flow changed from positive $3.5 million in 2022 to negative $111.6 million in 2023.
- Vaxcyte exercised an option in November 2023, generating $97.5 million of recognized revenue. A further $25 million installment was due within six months of exercise, and up to $60 million in regulatory milestone payments may become payable.
- Blackstone paid $140 million for Sutro’s specified 4% royalty interest in potential Vaxcyte product sales. Following a Vaxcyte license amendment, royalties on non-PCV products reverted to Sutro; the sold interest covers PCV products such as VAX-24 and VAX-31.
- BMS ended development of CC-99712, and EMD Serono ended development of M1231. Rights to CC-99712 reverted to Sutro. After year-end, in March 2024, BioNova terminated its STRO-001 option and development in Greater China; Sutro then suspended STRO-001 development.
- Shares issued and outstanding increased from 57.5 million at year-end 2022 to 61.0 million at year-end 2023. The filing reported 62.4 million shares outstanding as of March 20, 2024.
Outlook, commentary and key risks
Management estimated that available cash, cash equivalents and marketable securities would fund operations for at least 12 months following the filing date, but stated that additional financing will be needed to advance development and fund operations for the foreseeable future. Sutro warned that capital may not be available on acceptable terms and that it may need to delay, reduce or stop programs, or pursue partnerships or financing that dilute shareholders or surrender rights.
- Luvelta’s Phase 2/3 REFRαME-O1 trial began in June 2023. Part 1 was expected to enroll about 50 patients and was anticipated to be fully enrolled in the first half of 2024; Part 2 is planned to enroll approximately 516 patients. The filing describes an optional interim analysis for response rate and duration of response, with progression-free and overall survival endpoints for potential full approval.
- Management expected to begin enrollment in a registration-directed pediatric RAM-phenotype AML trial in the second half of 2024. It also planned an IND submission for luvelta in non-small cell lung cancer in the first half of 2024, and anticipated IND readiness for STRO-003 in 2024 and STRO-004 in 2025.
- Luvelta data are preliminary and from relatively small, non-registrational studies. In a reported Phase 1 subset of 43 patients with platinum-resistant ovarian cancer and FolRα TPS of at least 25%, the response rate was 28%, median duration of response 5.7 months and median progression-free survival 5.8 months. The filing cautions that interim results may change and may not predict pivotal-trial outcomes.
- Neutropenia was a prominent luvelta safety issue. In aggregated Phase 1 data, 64.6% of patients had Grade 3 or higher neutropenia; six Grade 5 safety events occurred, one assessed as probably related to luvelta. Pegfilgrastim reduced reported neutropenia in an exploratory cohort, but requires confirmation in ongoing trials.
- Major risks include clinical failure or delay, competition in ovarian cancer (including approved Elahere), need for substantial additional capital, reliance on collaborators, manufacturing scale-up and regulatory uncertainty for the cell-free platform, and potential safety issues. Sutro also highlighted patent, cybersecurity, data privacy, and third-party supply risks.
The financial statements received an unqualified audit opinion. The auditor identified the Blackstone royalty transaction and management’s estimates of future royalties and related interest as a critical audit matter. Management reported effective disclosure controls and internal control over financial reporting; the external auditor was not engaged to attest to ICFR effectiveness.
Most important facts for investors to verify
- Current cash runway and financing needs, including cash use after year-end and whether additional capital or partnering is required.
- Enrollment progress, dose selection and timing for REFRαME-O1, plus whether pivotal results support regulatory filings.
- Whether the preliminary luvelta efficacy and safety findings, including neutropenia management, are reproduced in larger controlled trials.
- Actual timing and status of the planned pediatric AML trial and luvelta NSCLC IND, and STRO-003/STRO-004 IND plans.
- Terms, timing and conditions of the remaining Vaxcyte option installment and potential milestones, and the assumptions underlying the $149.1 million deferred royalty obligation.
- Post-year-end loan repayment, BioNova termination, subsequent share issuance and any other material changes to liquidity, pipeline priorities or outstanding shares.