ImmunoGen's lead product candidate, the clinical-phase mirvetuximab soravtansine (IMGN853), will be studied with Merck & Co.’s Keytruda® (pembrolizumab) as a combination therapy for folate receptor alpha (FRα)-positive ovarian cancer.

The value of the clinical research collaboration was not disclosed by ImmunoGen, which announced the partnership today.

ImmunoGen said it will add the combination to its ongoing Phase IB/II FORWARD II trial, in which the company is assessing mirvetuximab soravtansine for FRα-positive ovarian cancer in separate combinations with other anticancer agents. Those agents include Johnson & Johnson/Janssen’s Doxil® (pegylated liposomal doxorubicin), Roche/Genentech’s Avastin® (bevacizumab), and the chemotherapy drug carboplatin.

Mirvetuximab soravtansine is also under study as a single agent for pretreated FRα-positive ovarian cancer in the Phase II FORWARD I trial. Results from that trial are intended to support an Accelerated Approval review pathway for the candidate.

Mirvetuximab soravtansine contains a monoclonal antibody designed to enable its binding to FRα-positive tumor cells with ImmunoGen's DM4, a maytansinoid cancer-killing agent, attached to kill these cells. According to ImmunoGen, ADCs with maytansinoids have been found in preclinical studies to enhance maturation and activation of the immune system’s dendritic cells, which stimulate antitumor responses.

In November, ImmunoGen presented positive Phase I results showing two of 10 (90%) platinum-resistant ovarian cancer patients with high levels of FRα had a complete response on treatment with mirvetuximab soravtansine, while another seven patients showed partial responses. When six patients with medium levels of FRα and four with low levels were included, the overall response rate was 50%.

Mirvetuximab soravtansine is also being evaluated as a potential treatment for other solid tumors, such as in endometrial and lung cancers.

ImmunoGen said the collaboration with Merck could be expanded to include a Phase III clinical trial.

Keytruda is a humanized monoclonal antibody that works by blocking interaction between the programmed death receptor-1 (PD-1) and its receptor ligands, PD-L1 and PD-L2—thus increasing the immune system’s ability to fight cancer in cells that produce the pigment responsible for color in the skin.

The FDA approved Keytruda in 2014 as the first PD-1 inhibitor indicated to treat unresectable or metastatic melanoma following treatment with ipilimumab. Keytruda is also indicated for patients who are mutation positive for the BRAF V600 inhibitor.

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