FDA Grants Fast Track Designation to STRO-002 in Select Patients With Advanced Ovarian Cancer

STRO-002 has received a fast track designation from the FDA for the treatment of patients with platinum-resistant epithelial ovarian, fallopian tube, or primary peritoneal cancer who have previously undergone treatment with 1 to 3 lines of systemic therapy, according to a press release from drug developer, Sutro Biopharma Inc.¹

The folate receptor α (FolRα)–targeting antibody-drug conjugate is currently being explored in phase 1 trials for the treatment of endometrial and ovarian cancers.

“We are pleased with the FDA’s decision to grant fast track designation for STRO-002 and welcome the opportunity to have more frequent interactions with the agency,” Arturo Molina, MD, MS, chief medical officer at Sutro Biopharma, said in a press release. “We continue to be enthused by the potential of the STRO-002 program, which has shown encouraging preliminary activity and tolerability in our phase 1 dose-escalation study in ovarian cancer, and plan to continue to work with the FDA to potentially accelerate our clinical and regulatory efforts.”

Early data from a phase 1 study (NCT03748186) read out in April 2020 and indicated that 62% of patients with heavily pre-treated ovarian cancer who received STRO-002 experienced a reduction in CA-125 equaling 50% or more or to a normalized level.² Additionally, 35% of patients who were evaluable for progression had stayed on the study for more than 24 weeks, with 11 patients continuing the study at a dose of 5.2 mpk who had not yet reached 24 weeks. Investigators also reported that 75% of patients who had initial post-baseline scans achieved stable disease or a partial response (PR). All evaluable patients who achieved a 50% or more reduction in CA-125 or normalization experienced confirmed or unconfirmed stable disease or a PR; all of these patients are still on the study.

“The preliminary evidence of anti-tumor activity we observed is encouraging, particularly in this heavily pre-treated patient population,” principal investigator Wendel Naumann, MD, a gynecologic oncologist at Levine Cancer Institute, said in a press release. “With limited therapeutic options for these patients, we are excited to continue to advance this clinical program to further investigate its therapeutic potential.”

Patients who enrolled to the open-label, dose-escalation study (n = 30) were treated at a dose level of 2.9 mpk or more. In total, investigators reported 1 confirmed PR at 36 weeks, 5 patients who achieved stable disease, and 7 who have ongoing unconfirmed stable disease as of the 6-week assessment point.

The agent was noted as being generally well tolerated, with patients primarily experiencing low-grade adverse effects (AEs; grade 1/2, 89%). The use of prophylactic corticosteroid eye drops have not been necessary during the study. Grade 2 treatment-emergent AEs included fatigue, neutropenia, arthralgia, diarrhea, peripheral neuropathy, and myalgia. Additionally, there was 1 reported case of grade 4 neutropenia, although investigators noted that all neutropenias were reversible within 1 week.

A dose-expansion portion of the trial was planned to start in the second half of 2020. Although investigators have not yet determined the maximum-tolerated dose, they are currently investigating the 5.2 and 6.0 mpk dose levels to decide on the recommended phase 2 dose.

“Receiving Fast Track designation is an important recognition for STRO-002 as a potentially best-in-class FolRα ADC for women with ovarian cancer. We look forward to further collaboration with the FDA to bring this potentially important therapeutic option to women in advanced stages of their disease with limited treatment options,” Bill Newell, chief executive officer at Sutro Biopharma, said in a statement.

References

1. Sutro Biopharma Announces STRO-002 FDA Fast Track Designation for Patients with Advanced Ovarian Cancer. News release. Sutro Biopharma Inc. August 18, 2021. Accessed August 18, 2021. https://prn.to/3iW9A6M
2. Sutro Biopharma Announces Encouraging Interim Phase 1 Clinical Data for a Dose Escalation Study of STRO-002 Antibody-Drug Conjugate in Ovarian Cancer. News release. Sutro Biopharma Inc. April 27, 2020. Accessed August 18, 2021. https://bit.ly/3sptUAE