Sutro Biopharma Stock (STRO): Why The Price Substantially Fell Today

By Amit Chowdhry ● Jan 6, 2022
  • The stock price of Sutro Biopharma, Inc. (NASDAQ: STRO) fell by over 29% during intraday trading today. This is why it happened.

The stock price of Sutro Biopharma, Inc. (NASDAQ: STRO) – a clinical-stage drug discovery, development, and manufacturing company focused on the application of precise protein engineering and rational design to create next-generation cancer and autoimmune therapeutics – fell by over 29% during intraday trading today. Investors are responding negatively to a clinical update from the company’s ongoing, fully enrolled, dose-expansion Phase 1 study of STRO-002, a folate receptor alpha (FolRα)-targeting antibody-drug conjugate (ADC), for patients with advanced ovarian cancer. The discussion of the data will be held at an STRO-002 Virtual Event at 2 pm PT/5 pm ET today.

The dose-expansion cohort for ovarian cancer enrolled 44 patients who had experienced up to 3 prior lines of therapy. And as of the interim data cutoff date of Nov. 8, 2021, 43 patients had been randomized into dose levels starting at 4.3 mg/kg and 5.2 mg/kg, and one patient had not yet been dosed. 81% of the patients were platinum-resistant, and 63% and 65% of the patients had been treated previously with bevacizumab and PARP inhibitors, respectively. Of the 43 patients, 33 had at least one post-baseline scan and, therefore, were evaluable for RECIST v1.1 responses.

As of Nov. 8, 2021, the interim data cutoff date, the Best Overall Response (BOR) for evaluable patients were as follows (N=33):

— Dose-response was observed, with an ORR of 47% (8 PRs out of 17 patients), for patients who started at the 5.2 mg/kg dose level, unenriched for biomarker status.

— Higher FolRα expression levels using TPS are correlated with higher response rates.

— Based on the data, an enrichment approach of TPS > 25% FolRα expression may enable treatment of about 70% of the advanced ovarian cancer patient population.

— Safety signals from the 43 safety evaluable patients at the 5.2 mg/kg and 4.3 mg/kg starting dose levels were consistent with data from the dose-escalation cohort.

— Data from the STRO-002 dose-expansion cohort are expected to provide further information to inform regulatory discussions and a global registration strategy.

In addition to the STRO-002-GM1 Phase 1 clinical trial, a STRO-002 study for patients with ovarian cancer in combination with bevacizumab and a study for patients with endometrial cancer are both enrolling at sites in the United States and Europe. The nonclinical work to expand STRO-002 to non-small cell lung cancer (NSCLC) and potentially into other FolRα-expressing solid tumors is also ongoing.


“These interim data in the dose-expansion cohort showing deep responders in ovarian cancer patients treated with STRO-002 are compelling. Patients entered the study with progressive disease and were a heavily pre-treated population and had experienced up to three lines of prior treatment. The interim data show that STRO-002 could potentially improve the lives of an underserved ovarian cancer patient population.”

— Dr. R. Wendel Naumann, Professor & Director of Gynecologic Oncology Research, Associate Medical Director of Clinical Trials at Levine Cancer Institute, and an investigator on the STRO-002 study

“We are encouraged by the investigator interest in STRO-002 in the dose-expansion cohort, with full patient enrollment in under a year. These interim data underscore our confidence in STRO-002 as a potential therapeutic for patients with ovarian cancer, and we will continue to follow the patients who remain on treatment. With additional data continuing to mature, we expect to confirm our dosing regimen and our patient selection strategy based on FolRα expression. We plan to advance STRO-002 into the next phase of clinical development and leverage our Fast Track designation for continuous engagement with the FDA.”

— Dr. Arturo Molina, Chief Medical Officer of Sutro

Disclaimer: This content is intended for informational purposes. Before making any investment, you should do your own analysis.