On March 12, 2017 ImmunoGen, Inc. (Nasdaq: IMGN), a leader in the expanding field of antibody-drug conjugates (ADCs) for the treatment of cancer, reported that data from a mirvetuximab soravtansine (IMGN853) Phase 1 biopsy expansion cohort demonstrate that archival tumor tissue can reliably identify patients with folate receptor alpha (FRα)-positive platinum-resistant ovarian cancer (Press release, ImmunoGen, MAR 12, 2017, View Source [SID1234518091]). These data will be presented at the Society of Gynecologic Oncology (SGO) Annual Meeting, which is being held March 12-15 in National Harbor, MD.

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"In the Phase 3 FORWARD I registration trial for mirvetuximab soravtansine, FRα expression for patient selection is being assessed based on archival tumor tissue samples," said Anna Berkenblit, M.D., Vice President and Chief Medical Officer of ImmunoGen. "The results being presented at SGO support this strategy to select patients for our Phase 3 FORWARD I trial. More broadly, the data being presented confirm that in this heavily pretreated cohort, mirvetuximab soravtansine is well tolerated and that the higher the FRα expression, the greater the anti-tumor activity."

The objectives of the biopsy expansion cohort were to:

Characterize FRα expression in archival tumor tissue and in pre- and post-treatment biopsy samples obtained from a heterogeneous population of relapsed epithelial ovarian cancer (EOC) patients;
Determine the concordance rate between archival tissue and pre-treatment biopsy FRα expression levels; and
Compare changes in FRα expression levels before and after treatment with mirvetuximab soravtansine in biopsy samples.
In the biopsy expansion cohort, a total of 27 heavily pretreated patients (including patients with up to 11 prior therapies) were enrolled based on FRα expression levels in archival tumor tissue. Patients underwent a pre-treatment biopsy prior to receiving mirvetuximab soravtansine and a post-treatment biopsy after two doses of mirvetuximab soravtansine.

A comparison of FRα levels in pre-treatment biopsies versus archival samples supports the use of archival tumor tissue for patient selection. Of the 21 evaluable pre-treatment samples, 15 met the eligibility criterion for the biopsy expansion cohort (≥ 25% cells with ≥ 2+ intensity), resulting in a 71% concordance with archival tumor tissues. Twenty-two percent (22%) of patients (6/27) did not have pre-treatment biopsies evaluable for FRα immunohistochemistry due to insufficient tumor cells present in the specimens. Additionally, biopsies taken prior to and following two doses of mirvetuximab soravtansine showed similar FRα expression levels. The findings also support the use of a pre-treatment biopsy for patient selection if archival tumor tissue is not available for evaluation.

The safety profile of the cohort was consistent with that previously reported for mirvetuximab soravtansine-treated EOC patients across the Phase 1 study, with predominately Grade 1 and 2 adverse events. Based on FRα expression in both archival and pre-treatment biopsies, the data also demonstrated that anti-tumor activity increased with higher FRα expression levels.

Presentation

Title: "Characterization of folate receptor alpha (FRα) expression in archival tumor and biopsy samples in a phase I study of mirvetuximab soravtansine, a FRα-targeting antibody-drug conjugate (ADC), in relapsed epithelial ovarian cancer patients" (abstract #61)

The findings will be presented during featured poster presentation discussion sessions:

Monday, March 13, 3:30-5:00pm ET
Tuesday, March 14, 3:30-4:30pm ET
Additional information can be found at www.sgo.org.

About Mirvetuximab Soravtansine

Mirvetuximab soravtansine (IMGN853) is the first FRα-targeting ADC. It uses a FRα-binding antibody to target the ADC specifically to FRα-expressing cancer cells and a potent anti-tumor agent, DM4, to kill the targeted cancer cells.

Mirvetuximab soravtansine is ImmunoGen’s lead program and is in Phase 3 testing (the FORWARD I trial) as a single agent for the treatment of platinum-resistant ovarian cancer. The candidate is also being assessed in combination regimens for both platinum-resistant and platinum-sensitive disease in Phase 1b/2 FORWARD II trial.