A first patient has been dosed in the dose-expansion cohort of the Phase I study with STRO-002, a folate receptor alpha (FolRα) targeting antibody-drug conjugate (ADC) for the potential treatment of ovarian cancer.

The drug was developed internally by researchers at Sutro Biopharma based on the company’s proprietary and integrated cell-free protein synthesis platform XpressCF® and site-specific conjugation platform XpressCF+™.

Lainie P. Martin, M.D.; Leader, Gynecology/Oncology Program Associate Professor of Medicine at the Hospital of the University of Pennsylvania Dr. Martin is a Penn Medicine physician and an investigator on the STRO-002-GM1 study. Photo courtesy: © 2020 – 2021, Penn Medicine, Philadelphia, PA/The Trustees of the University of Pennsylvania.

Ovarian cancer
With ovarian cancer often diagnosed in the late stages, recurrence is high in this patient population. Early identification can range from knowing the vague symptoms associated with ovarian cancer to prophylactic surgical removal of at-risk tissue. Standard treatment for ovarian cancer is surgery followed by combination chemotherapy. Although advances are being made, ovarian cancer remains the most fatal female gynecologic cancer. Hence, there is a large unmet medical need and research is ongoing in trying to find novel diagnostics as well as better treatment options.[1]

The phase I study is an open-label, multicenter, dose-escalation trial with dose expansion of STRO–002, which has completed enrollment. Follow-up is ongoing and will continue to evaluate the safety, tolerability, and preliminary anti-tumor activity of STRO-002 in adults with advanced epithelial ovarian cancer, including fallopian and primary peritoneal cancer.

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The dose-expansion cohort will assess the efficacy, safety, and tolerability of STRO-002 at 4.3 and 5.2 mg/kg, given every 3 weeks in patients with ovarian cancer. The dose-expansion cohort for FolRα-selected endometrial cancer is planned for later this year.

“We are pleased to advance the clinical development of STRO-002 into dose-expansion studies. Results from our STRO-002 dose escalation in a heavily pre-treated ovarian cancer patient population demonstrated improved outcomes in RECIST response and duration of response,” noted Arturo Molina, M.D., M.S., FACP, the Chief Medical Officer of Sutro Biopharma.

“[We plan] to expand the study to approximately 35 clinical sites in the U.S. and Europe. We are hopeful that the dose-expansion study will validate the preliminary signs of efficacy we have seen in dose-escalation and provide valuable data on the treatment paradigm and patient population that will benefit from treatment, bringing us one step closer to offering an important new potential treatment option to ovarian cancer patients.”

“STRO-002 continues to be well-tolerated and we have observed encouraging preliminary activity in patients with advanced platinum-resistant and refractory ovarian cancer,” said Lainie Martin, M.D., Leader of Gynecology/Oncology Program at Hospital of the University of Pennsylvania and an investigator on the STRO-002-GM1 study.

“We are excited to be part of the STRO-002-GM1 dose-expansion study and to provide additional clinical data to show the potential of this therapeutic for ovarian patients with limited treatment options,” Martin further noted.

Two patient cohorts
The dose-expansion study includes two patient cohorts, advanced epithelial ovarian cancer, and endometrial cancer. The ovarian cancer cohort currently enrolling includes patients with the platinum-resistant disease and have received 1-3 prior regimens or platinum-sensitive patients that have received 2-3 prior treatment regimens.

Patients in the dose-expansion cohort of the STRO-002-GM1 Phase 1 study will be randomized 1:1 and treated with either 4.3 or 5.2 mg/kg STRO-002 intravenously once every three weeks. Patients will not be pre-selected for FolRα expression and fresh or archival tumor tissue sample is required for immunohistochemistry (IHC) analysis of FolRα expression.

Clinical trials
Study of STRO-002, an Anti-Folate Receptor Alpha (FolRα) Antibody Drug Conjugate in Ovarian & Endometrial Cancers [NCT03748186]

Reference
[1] Stewart C, Ralyea C, Lockwood S. Ovarian Cancer: An Integrated Review. Semin Oncol Nurs. 2019 Apr;35(2):151-156. doi: 10.1016/j.soncn.2019.02.001. Epub 2019 Mar 11. PMID: 30867104.

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