ImmunoGen is poised to solve a major unmet medical need in ovarian cancer


On 26 January, ImmunoGen announced that the first patient in its pivotal Phase III study investigating mirvetuximab soravtansine as a single agent treatment in ovarian cancer was dosed, positioning its novel antibody-drug conjugate (ADC) well within the late-stage pipeline.

If ImmunoGen can replicate the early results first presented at ASCO 2016, it has the potential to solve a major unmet medical need for patients with platinum-resistant disease.

Once a patient becomes resistant to platinum-based chemotherapy regimens, the efficacy and duration of response with current treatment options are highly limited. The FORWARD I study aims to recruit 333 ovarian cancer patients and randomise them 2:1 to receive either mirvetuximab soravtansine or the physician’s choice of single-agent chemotherapy (pegylated liposomal doxorubicin, toptotecan, or weekly paclitaxel). The primary endpoint of progression-free survival (PFS) will be assessed in the entire study population and in the subset of patients with high folate receptor alpha (FRA) expression.

At ASCO 2016, ImmunoGen demonstrated encouraging single agent activity in 46 platinum-resistant ovarian cancer patients, with a confirmed objective response rate (ORR) of 26% with one complete response (CR), 11 partial responses (PR), a median PFS of 4.8 months, and a median duration of response (DOR) of 19.1 weeks.

The experimental treatment was well tolerated and 28% of patients required dose modifications due to low-grade ocular adverse events (AE). These eye-related toxicity concerns decreased in patients enrolled in the latter part of the study, which was attributed to more effective management procedures. 

In a subgroup analysis of 16 patients with one to three prior lines of therapy with medium to high folate receptor alpha expression, ImmunoGen saw a 44% ORR, a median PFS of 6.7 months, and a median DOR of 26.1 weeks.

GlobalData’s primary research has confirmed that the response rate of 44% in this ovarian cancer patient segment is unprecedented, especially with single-agent activity. The company has designed its Phase III FORWARD I study to enroll patients with platinum-resistant ovarian cancer with one to three prior therapies with medium or high levels of FRA expression.

Mirvetuximab soravtansine is an antibody drug conjugate that selectively targets cells that express FRA and delivers cytotoxic payload DM4 to kill cells. Unlike previous FRA antibodies such as Morphotek’s farletuzumab, Immunogen’s asset does not solely rely on the patient’s immune system to kill cancer cells. 

This small nuance is important, especially in heavily pre-treated patients whose immune systems can be compromised due to previous drug treatments and their overall health status. Furthermore, the FRA pathway is not important for ovarian cancer cell survival. Even if it is blocked, the cancer still grows.

Key opinion leaders (KOL) interviewed by GlobalData say this is a major differentiator for mirvetuximab soravtansine, and the question now becomes how much FRA expression is necessary for it to become a valuable target for a precision medicine treatment?

ImmunoGen’s long-term growth prospects in the ovarian cancer space are supported by early stage investigations looking to improve single agent mirvetuximab soravtansine’s activity by combining it with Roche / Genentech’s approved ovarian cancer angiogenesis inhibitor Avastin (bevacizumab); Merck and Co.’s immune checkpoint inhibitor blockbuster Keytruda (pembrolizumab); the first-line standard of care chemotherapy carboplatin; and pegylated liposomal doxorubicin.

These combinations are currently being investigated in the ongoing Phase Ib/II FORWARD II trial. Their anticipated increased efficacy compared to the single agent regimen and current standards of care could firmly entrench mirvetuximab soravtansine earlier in the treatment paradigm, especially if the combinations are well tolerated.

ImmunoGen has a lot of work ahead, but the future is bright for its novel ADC, which could simultaneously solve a major problem for platinum-resistant recurrent ovarian cancer patients and represent a major victory for the precision medicine movement.

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