Sutro Biopharma — Third Quarter 2026 Earnings Summary

Financial Performance:

• Revenue for the quarter ended September 30, 2026, was $9.1 million, a decrease from $9.7 million in the same period in 2025; revenue was primarily related to the Astellas collaboration.
• Total Research & Development (R&D) and General & Administrative (G&A) expenses were $31.0 million for the quarter, compared to $48.6 million in the prior year period.
• Specific operating expenses for the quarter included R&D of $23.5 million, G&A of $7.5 million, and restructuring costs of $0.02 million, totaling $31.1 million in operating expenses.
• Net loss for the quarter was $31.5 million, an improvement from a net loss of $56.9 million in the prior year period.
• Loss per share (basic and diluted) was $1.90, compared to $6.66 in the prior year period.
• Cash, cash equivalents, and marketable securities totaled $142.2 million as of September 30, 2026, down from $164.3 million as of June 30, 2026.
• Accounts receivable increased to $12.8 million as of September 30, 2026, from $4.0 million as of December 31, 2025.
• Deferred revenue decreased to $10.1 million as of September 30, 2026, from $12.6 million as of December 31, 2025.
• The company reported a non-cash interest expense of $10.2 million related to the sale of future royalties for the quarter.

Guidance and Future Outlook:

• The company expects its current cash runway to support operations into the first half of 2028.
• STRO-004 (TF-targeting ADC) plans to provide the next clinical update and initiate expansion cohorts in select indications in the first half of 2027.
• STRO-006 (ITGB6-targeting ADC) anticipates an initial Phase 1 data update in the second half of 2027.
• STRO-227 (PTK7-targeting dual-payload ADC) is advancing toward the initiation of a Phase 1 clinical trial in early 2027.

Business Segments and Product Lines:

• STRO-004: Evaluated in the Phase 1 STRIVE-01 study; initial dose escalation in 49 heavily pretreated patients showed encouraging clinical activity with confirmed and ongoing unconfirmed partial responses across three tumor types and favorable tolerability.
• STRO-006: First patient dosed in October 2026 in a Phase 1 study for advanced or metastatic solid tumors; dose-escalation will enroll patients with ITGB6-expressing tumor types including head and neck, non-small cell lung, esophageal/gastric, colorectal, endometrial, urothelial, and breast cancers.
• STRO-227: A DAR10 dual-payload ADC combining MMAE and exatecan payloads designed to widen the therapeutic index and overcome resistance.
• Astellas Collaboration: Two dual-payload immunostimulatory ADC (iADC) programs are advancing; the TROP2-targeting program continues active dosing, and the B7-H3-targeting program began dosing, triggering a $10 million milestone payment received by Sutro in October 2026.

Market and Competitive Landscape:

• Sutro is positioning its next-generation ADC platform to deliver single- and dual-payload ADCs with a wider therapeutic index and the potential to overcome resistance to single-payload ADCs.
• The company aims to expand its portfolio of ADCs to target large oncology markets with limited treatment options.

Risks and Challenges:

• Forward-looking statements highlight risks related to the ability to advance product candidates, receipt of regulatory approvals, market size, clinical trial execution, supply chain, and manufacturing facilities.
• Risks include the timing and results of preclinical and clinical trials, the ability to fund development activities, intellectual property protection, and the impact of geopolitical conflicts, inflation, and interest rate changes.

Management Commentary and Tone:

• CEO Jane Chung stated the company delivered on its commitment to advance next-generation ADCs, with two programs entering the clinic in less than a year and a third following in early 2027.
• Management expressed confidence in STRO-004's potential to deliver meaningful clinical benefit based on early data.
• The CEO highlighted the company's proficiency in translating platform innovation into a growing pipeline and its ability to deliver differentiated dual-payload ADCs.

Other Key Points:

• Sutro appointed Lucas Donigian as Senior Vice President, Business Development, in September, bringing over 20 years of biotechnology industry experience.
• Initial STRO-004 clinical safety and pharmacokinetic findings, along with preclinical updates on STRO-006 and STRO-227, were presented at the 17th Annual World ADC Conference in October 2026.
• Management is scheduled to participate in the UBS Global Biopharma Conference (November 17), Jefferies Global Healthcare Conference (November 18), and Piper Sandler 38th Annual Healthcare Conference (December 2).
• The company holds a deferred royalty obligation related to the sale of future royalties of $249.3 million as of September 30, 2026.