Sutro Biopharma, Inc.

What they do

Sutro Biopharma is a clinical-stage oncology company focused on discovering and developing site-specific and novel-format antibody drug conjugates (ADCs), including bispecific, immunostimulatory, and dual-payload ADCs. Its proprietary platforms, XpressCF and XpressCF+, enable rapid evaluation of protein structure-activity relationships to create homogeneous product candidates. The company's lead wholly-owned candidate, STRO-004, targets tissue factor (TF) and is in Phase 1 trials for solid tumors. Sutro also has preclinical programs including STRO-006 (targeting integrin avb6) and STRO-227 (a dual-payload ADC targeting PTK7), and collaborates with major pharmaceutical partners on multiple programs.

Revenue drivers

• Collaboration revenue (Astellas, Merck, Celgene/BMS, EMD Serono) — Sutro generates revenue primarily from its multi-target collaborations with Astellas (iADCs), Merck (cytokine derivatives), Celgene/BMS (BCMA ADC), and EMD Serono (MUC1-EGFR ADC). Revenue from these collaborations varies by year, with annual total revenue ranging from $62.0M to $153.7M over 2021–2025.
• Platform technology licenses and services (Vaxcyte) — Sutro's XpressCF platform supports vaccine development for Vaxcyte, providing potential research and development fees or royalties. Specific revenue amounts from this collaboration are not separately disclosed.
• Wholly-owned product candidates (STRO-004, STRO-006, STRO-227) — These are not yet generating revenue; the company is investing in their development with potential future commercialization or out-licensing.

Recent performance

For Q2 2026 (quarter ended June 30, 2026), Sutro reported revenue of $9.8 million, down from $14.5 million in Q1 2026 and $11.6 million in Q4 2025. The company posted a net loss of $191.0 million for 2025 (diluted EPS $ -22.49) and had a negative shareholder equity of $103.3 million as of June 30, 2026. Cash and equivalents were $54.3 million at June 30, 2026, but the company also reported $164.3 million in cash, cash equivalents, and marketable securities in its earnings release. Operating cash flow was negative $177.2 million in 2025.

Strategy

Sutro's strategy is to leverage its XpressCF and XpressCF+ platforms to rapidly develop a portfolio of wholly-owned and partnered ADCs, focusing on clinically validated targets where standard of care is suboptimal. The company prioritizes advancing STRO-004 as its lead candidate, with a goal of best-in-class positioning, while also progressing STRO-006 and STRO-227 into the clinic. Sutro is also expanding its pipeline through partnerships, such as the Astellas collaboration for dual-payload iADCs, and may out-license programs depending on capital. Management emphasizes execution speed and dose optimization to maximize therapeutic index and enable combination therapies.

Risks

• Clinical development risk for STRO-004 — The Phase 1 trial is ongoing; maximum tolerated dose not yet defined, and initial data are early signals, not confirmed efficacy.
• Limited cash runway — With $164.3 million in cash and securities as of June 30, 2026, the company expects to fund operations into at least Q2 2028, but negative cash flow and negative equity raise going-concern risk.
• Dependence on collaborations — Revenue depends heavily on collaborations with Astellas, Merck, Celgene/BMS, and EMD Serono; termination or delays could materially affect financials (as seen with a terminated agreement in March 2026).
• Preclinical and regulatory milestones — STRO-006 IND may be filed in 2026 and STRO-227 IND in late 2026/early 2027; any delays could impact pipeline progression and timelines.

Outlook

Management expects to report initial data from the STRO-004 Phase 1 trial in mid-2026, and as of August 2026 has already reported encouraging early activity. They are optimizing the STRO-004 dose between 4-5 mg/kg, with no maximum tolerated dose yet defined. STRO-006 is on track to enter the clinic in Q3 2026, and a second dual-payload iADC program under the Astellas collaboration is expected to enter the clinic in the second half of 2026. Sutro also anticipates IND filing for STRO-227 later this year or early 2027.