Sutro's continued PhI data readouts indicate improving response in ovarian cancer. What's next?
The San Francisco-based biotech announced Thursday afternoon that patients with heavy previous treatment continued to see improvements as they remained on the drug, with one individual achieving a complete response after more than a year. With the new data in hand, Sutro plans to begin a dose-expansion cohort in January, which could be followed by an accelerated approval application in the second half of 2021.
Investors greeted the news happily, sending shares up about 22% after Thursday’s closing bell.
Sutro’s experimental drug in question, called STRO-002, is a folate receptor alpha (FolRα) targeting antibody-drug conjugate. The candidate was being studied as a monotherapy in 34 ovarian cancer patients who collectively underwent a median of 6 previous therapies, and of those, 31 met the criteria to be evaluated at the Oct. 30 data cutoff.
Though researchers had looked at 33 patients in their last interim look on Aug. 30, the overall response rate and number of patients registering a response increased. As of the newest October readout, 10 of 31 individuals achieved at least a partial response, including one whose cancer disappeared entirely. The program also saw 23 of 31 patients achieve disease control after 12 weeks, and 18 of 31 after 16 weeks.
Patients remained on the treatment for a median of 19 weeks, and on the readout date 10 were still taking the treatment.
In terms of safety, Sutro said the therapy continued to be well-tolerated, with 86% of treatment-related side effects clocking in at Grade 1 or 2. Stifel’s Konstantinos Aprilakis noted there was one additional case of Grade 3 neuropathy, but saw the safety profile as “highly consistent” with the August update.
The consensus among Aprilakis and other analysts sings the praises of the continued efficacy of the data, especially given the sheer amount of treatments patients had undergone in the past. Aprilakis said the complete response was “a remarkable achievement” while Cowen’s Boris Peaker wrote the data “exceeded investor expectations.”
Wedbush’s David Nierengarten also chimed in, saying Thursday’s announcement bodes well for future studies.
“Importantly, responses appear to deepen with time,” he wrote to investors. “Given the earlier intervention with STRO-002, we expect STRO to achieve an even more compelling efficacy profile than observed in the escalation portion of the study.”
Moving forward, Sutro is planning the dose-escalation cohort to begin in January with a data readout expected sometime in the first half of next year. If all goes according to plan, Aprilakis expects a decision on whether to file for accelerated approval before 2021 is out.