The Phase 3 SOROYA trial demonstrated  promising response rates with mirvetuximab soravtansine, previously known as  IMGN853, in patients with platinum-resistant ovarian cancer and high folate receptor–alpha expression. Mirvetuximab soravtansine is a first-in-class antibody-drug conjugate comprising a folate receptor alpha (FRα)-binding antibody, cleavable linker, and the maytansinoid payload DM4, a potent tubulin-targeting agent to kill the targeted cancer cells.

Full results from the pivotal SORAYA trial evaluating the efficacy and safety of mirvetuximab soravtansine monotherapy in patients with folate receptor alpha (FRα)-high platinum-resistant ovarian cancer who have been previously treated with bevacizumab (Avastin®; Genentech/Roche) were presented by Ursula A. Matulonis, MD, Chief of the Division of Gynecologic Oncology at the Dana-Farber Cancer Institute, Professor of Medicine at the Harvard Medical School, and SORAYA Co-Principal Investigator in the late-breaking abstract plenary session on Saturday, March 19, 2022 at the Society of Gynecologic Oncology (SGO) 2022 Annual Meeting in Phoenix, AZ.

The study results showed that the trial met its primary endpoint with confirmed objective response rate (cORR) of 32.4%, including 5 complete responses; updated median duration of response (MDR) of 6.9 Months.  The trial results confirmed that mirvetuximab soravtansine offers a meaningful anti-tumor activity, consistent safety, and favorable tolerability in FRα-High Platinum-Resistant Ovarian Cancer.

Based on these results, Immunogen a Biologics License Application (BLA) Submission Expected this Month Demonstrated Meaningful Anti-Tumor Activity, Consistent Safety, and Favorable Tolerability in FRα-High Platinum-Resistant Ovarian Cancer

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Limited treatment Options
“Patients with platinum-resistant ovarian cancer have limited treatment options, and these are associated with low response rates and significant toxicity,” said Ursula Matulonis, MD, Chief of the Division of Gynecologic Oncology at the Dana-Farber Cancer Institute, Professor of Medicine at the Harvard Medical School, and SORAYA Co-Principal Investigator.

“With an objective response rate of 32.4%, far exceeding that seen with current therapies, and a median duration of response approaching seven months, mirvetuximab soravtansine continues to demonstrate impressive efficacy in patients with platinum-resistant disease who have already received bevacizumab. The anti-tumor activity and consistent safety and tolerability data from the SORAYA trial further underscore the potential of mirvetuximab soravtansine, if approved, to become a practice-changing, biomarker-driven standard of care for these patients.”

Ursula A. Matulonis, MD, Chief of the Division of Gynecologic Oncology at the Dana-Farber Cancer Institute, Professor of Medicine at the Harvard Medical School, and SORAYA Co-Principal Investigator

Trial design
The SORAYA -trial is a single-arm study of mirvetuximab soravtansine in patients with platinum-resistant ovarian cancer whose tumors express high levels of FRα and who have been treated with one to three prior regimens – at least one of which included bevacizumab.

The primary endpoint for the study is confirmed objective response rate (ORR) as assessed by investigator and the key secondary endpoint is duration of response (DOR).

The ORR was also assessed by blinded independent central review (BICR). The study is designed to rule out a 12% ORR, based on expected outcomes of 4% to 13% with available single agent chemotherapy.

Data previously generated in a post-hoc pooled analysis of seventy patients from prior studies of mirvetuximab soravtansine in platinum-resistant disease formed the basis for the design of SORAYA, with an investigator-assessed ORR of 31.4%, median DOR of 7.8 months, and median progression-free survival (PFS) of 4.4 months.

Key Findings
The SORAYA trial enrolled 106 patients with a median of three prior lines of therapy; 51% had three prior lines of therapy and 48% had one to two prior lines of therapy. All patients received prior bevacizumab; 48% of patients received a prior PARP inhibitor (PARPi). Confirmed ORR by investigator was 32.4% (95% confidence interval [CI]: 23.6%, 42.2%), including five complete responses (CRs). ORR by BICR was 31.6% (95% CI: 22.4%, 41.9%), including five CRs.

Response rates were consistent regardless of number of prior lines of therapies or prior PARPi. Following 1-2 prior lines of therapy: ORR by investigator was 35.3% (95% CI: 22.4%, 49.9%) and in patients who had received 3 prior lines of therapy: ORR by investigator was 30.2% (95% CI: 18.3%, 44.3%).

Prior exposure with a PARP inhibitor demonstrated ORR by investigator was 38.0% (95% CI: 24.7%, 52.8%). Without prior PARPi exposure the ORR by investigator was 27.5% (95% CI: 15.9%, 41.7%).

The median DOR was 6.9 months (95% CI: 5.6, 8.1) by investigator as of the March 3, 2022 data cut-off. The median PFS was 4.3 months (95% CI: 3.7, 5.1) by investigator and 5.5 months (95% CI: 3.8, 6.9) by BICR.

Overall, the study results showed that mirvetuximab soravtansine was well-tolerated, consistent with the known safety profile seen in more than 700 patients treated in the broader mirvetuximab program. Treatment-related adverse events led to dose reductions in 19% of patients, dose delays in 32% of patients, and discontinuations in 7% of patients. The most common treatment-related adverse events were low-grade and generally reversible, including blurred vision (41% all grade; 6% grade 3), keratopathy (36% all grade; 8% grade 3+), and nausea (29% all grade; 0% grade 3).

“We are thrilled with the SORAYA results, which are remarkably consistent with data previously generated with mirvetuximab soravtansine in a heavily-pretreated population of platinum-resistant ovarian cancer patients that included prior exposure to bevacizumab. Based on the impressive anti-tumor activity, durability of response, and safety profile observed in SORAYA, we believe mirvetuximab has the potential to displace single-agent chemotherapy as the standard of care for FRα-high platinum-resistant ovarian cancer,” noted Anna Berkenblit, MD, Senior Vice President and Chief Medical Officer of ImmunoGen.

“We are very grateful for all of the patients and physicians who committed their time and effort to this study, and with these positive results, we expect to submit the BLA for mirvetuximab this month to support potential accelerated approval in the US this year,” Berkenblit added.

“The strength and consistency of the SORAYA data give us confidence in a positive outcome in the ongoing confirmatory MIRASOL trial, intended to support the potential full approval of mirvetuximab, with top-line data anticipated in the third quarter,” she concluded.

In addition to full results from the pivotal SORAYA trial, trial in progress posters from the MIRASOL and PICCOLO trials of mirvetuximab soravtansine in ovarian cancer and a Phase 2 investigator-sponsored combination trial of mirvetuximab with carboplatin in the neoadjuvant setting for patients with newly diagnosed ovarian cancer were also be presented.

Final data from the mirvetuximab plus bevacizumab platinum-agnostic combination, which were originally shared at ASCO 2021, will also be featured in a seminal presentation.

Clinical trials
A Study of Mirvetuximab Soravtansine in Platinum-Resistant, Advanced High-Grade Epithelial Ovarian, Primary Peritoneal, or Fallopian Tube Cancers With High Folate Receptor-Alpha Expression (SORAYA) – NCT04296890
A Study of Mirvetuximab Soravtansine vs. Investigator’s Choice of Chemotherapy in Platinum-Resistant, Advanced High-Grade Epithelial Ovarian, Primary Peritoneal, or Fallopian Tube Cancers With High Folate Receptor-Alpha Expression (MIRASOL) –NCT04209855
Mirvetuximab Soravtansine Monotherapy in Platinum-Sensitive Epithelial, Peritoneal, and Fallopian Tube Cancers (PICCOLO) – NCT05041257

Highlights of Prescribing Information
Bevacizumab (Avastin®; Genentech/Roche) (Prescribing Information)

Reference
[1] Matulonis UA, Lorusso D, Oaknin A, et al. Efficacy and safety of mirvetuximab soravtansine in patients with platinum-resistant ovarian cancer with high folate receptor alpha expression results from the SORAYA study. Abstract 242 was presented at the 2022 SGO Annual Meeting on Womens’ Cancers; March 18-21, 2022; Phoenix, AZ.

Featured image: Ovarian Cancer. Photo courtesy: © 2016 – 2022 Fotolia/Adobe. Used with permission.

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