- ImmunoGen said Friday its leading therapeutic candidate failed to improve progression-free survival (PFS) in a Phase 3 ovarian cancer study, causing its stock to drop 50% upon market open and raising additional questions over the result's potential impact on other, ongoing studies involving the drug.
- The trial treated 366 patients with folate receptor alpha-positive, platinum-resistant ovarian cancer, randomly giving two-thirds its experimental antibody-drug conjugate, mirvetuximab soravtansine, in the third line. The remaining patients received chemotherapy as the control group.
- The treatment did not improve PFS, the study's primary endpoint, in either the entire study population or a pre-specified subgroup with higher expression levels of the folate receptor alpha protein. Company leaders argued the results were a narrow statistical miss, particularly for the high expression subgroup. The drug also missed on a secondary endpoint of overall survival.
ImmunoGen, a Waltham, Massachusetts-based biotech founded in 1981, has racked up an accumulated deficit of roughly $1.1 billion and still has no product revenue, according to its last quarterly filing with the Securities and Exchange Commission.
This antibody-drug conjugate, or ADC, is the leading prospect in ImmunoGen's pipeline. And this monotherapy study was, as one Wall Street analyst put it in a note last month, is "the key binary event" for filing for approval in the latter half of this year.
A variety of combination studies for ovarian cancer with mirvetuximab soravtansine are ongoing, testing it with Keytruda (pembrolizumab), Avastin (bevacizumab) and other therapies.
But those combination trials are largely contingent on the monotherapy study, dubbed FORWARD I, panning out, Cowen & Co.'s Boris Peaker remarked in a Feb. 8 note.
While it failed to reach the primary endpoint, the study showed statistical significance on improved overall response rates in the entire population. The experimental treatment group registered a 22% response rate compared to 12% for those treated with chemotherapy.
And those numbers were slightly better for the high expression subgroup, with the treatment posting a 24% response rate against 10% for those on chemo.
The company's chief medical officer Anna Berkenblit also focused on this subset in a statement, and one Wall Street analyst sees a focus on these patients as the most efficient path forward.
"If an additional trial is needed, we note that a potential path forward in a similar population as FORWARD-1, though with all [folate receptor alpha]-high patients, could achieve the fastest path to market," RBC Capital Markets analyst Kennen MacKay wrote in a March 1 note to investors.
This latest setback plunges ImmunoGen deeper into the red on the Nasdaq. A year ago, the stock was trading at about $11 per share. Since then, the share price has dropped nearly 80%, opening Friday at $2.38.