ASCO 2015: IMGN853 Demonstrates Single-Agent Activity for Patients With Platinum-Resistant Ovarian Cancer


Key Points

  • Once ovarian cancer becomes platinum-resistant, the usually second- and third-line setting response rates are about 15% to 20%.
  • Of 17 patient responses analyzed, 9 had an objective response.
  • The responses in six of the nine responsive patients were ongoing at the time of data cutoff, with five of these six patients on treatment for more than 15 weeks. 

In a phase I trial, the investigational agent mirvetuximab soravtansine (IMGN853) was found to be active in patients with platinum-resistant ovarian cancer. ImmunoGen, Inc, announced the first clinical findings of this folate-receptor alpha (FRα)-targeting antibody-drug conjugate at the 2015 ASCO Annual Meeting (Abstract 5518).

Study Background

Standard first-line therapy for ovarian cancer is a platinum-based regimen. Once the cancer becomes platinum-resistant, patients may receive single-agent therapy. Response rates with these agents in the second- and third-line setting are typically around 15% to 20%.

The findings reported at the ASCO Annual Meeting were from an ongoing phase I trial. Once the recommended phase II dose of IMGN853 was established during dose finding (reported in Abstract 5558), an expansion cohort was opened to assess the safety and activity of this antibody-drug conjugate specifically in the treatment of patients with FRα-positive platinum-resistant ovarian cancer. Approximately 80% of the patients screened have met the criteria for having FRα-positive disease.

A total of 22 patients were included in the analysis—2 from the dose-escalation phase of the trial and the 20 enrolled in the expansion cohort at the time of data cutoff for presentation. All had FRα-positive, platinum-resistant ovarian cancer, and had received IMGN853 at the recommended phase II dose (6.0 mg/kg, given every 3 weeks). All had previously received taxane as well as platinum therapy. Thirteen patients were still on study at the time of data cutoff.

Study Findings

The majority of adverse events reported were low grade (grade 1 or 2), with diarrhea, blurred vision, nausea, vomiting, fatigue, and abdominal pain as the most common treatment-emergent events reported (> 20% of patients).

Of the 22 patients, 17 were included in the efficacy analysis; the other 5 patients were still on study and had not yet reached their first assessment. Of these 17 patients, 9 had an objective response to treatment (8 partial responses, 1 complete response), for an overall response rate of 53%. The responses in six of these nine patients were ongoing at the time of data cutoff, with five of these six patients on treatment for more than 15 weeks.

“These initial clinical findings with IMGN853 in the treatment of patients with FRα-positive platinum-resistant ovarian cancer are highly encouraging,” commented Kathleen Moore, MD, Mai Eager Anderson Chair of Cancer Clinical Trials, at Stephenson Cancer Center, University of Oklahoma Health Sciences Center. “There is a significant need for new therapies for patients with ovarian cancer, including platinum-resistant disease.”

“Based on these findings, we are implementing a development plan designed to advance IMGN853 as quickly as possible, while also recognizing the potential to benefit the greatest number of patients,” commented Charles Morris, MB, ChB, MRCP, Executive Vice President and Chief Development Officer of ImmunoGen. “We’re preparing to initiate a phase II trial in late 2015 that will assess this [antibody-drug conjugate] as a single-agent treatment for patients with FRα-positive platinum-resistant ovarian cancer. It is possible that this trial could be used for registration in this patient population.”

Dr. Morris continued, “At the same time, we’re preparing to initiate testing of IMGN853 in combination regimens as a potential therapy for patients with less heavily pretreated ovarian cancer. We’re also continuing to explore this promising [antibody-drug conjugate] as a treatment for other types of FRα-positive solid tumors, including target-positive endometrial cancer. To complement our own research, ImmunoGen recently entered into a collaboration with the National Comprehensive Cancer Network® Oncology Research Program to investigate IMGN853 in additional preclinical and clinical studies.”

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.