CHICAGO (The Street) -- Oncothyreon (ONTY) came into this year's ASCO annual meeting hoping to show investors that the experimental breast cancer drug ONT-380 was effective and different from other therapies used to treat women with HER2-positive metastatic breast cancer.
Oncothyreon largely accomplished that goal. In a couple of posters presented Saturday, combinations of medicines including ONT-380 induced meaningful tumor shrinkage in breast cancer patients who entered the study because they were no longer responding to multiple prior therapies.
Perhaps most importantly, ONT-380, dosed as a relatively convenient pill, was able to demonstrate some effect on tumors that spread from the breast to the brain. Current drugs used to treat HER2-positive breast cancer aren't capable of treating brain metastases, which occur in about half of patients. ONT-380 was also relatively well tolerated, without reports of severe diarrhea that have caused concern about other HER2-blocking breast cancer drugs in development, most notably Puma Biotech's (PBYI) neratinib.
The ONT-380 data presented Saturday were derived from a small study and the contribution of Oncothyreon's drug to the response observed in breast cancer patients is a bit difficult to tease out because of the combination therapy. Investors won't be forecasting blockbuster sales of ONT-380 just yet, but then, Oncothyreon's market value of $350 million is still small enough to grow considerably over time if the drug continues to show positive progress.
Oncothyreon shares closed Friday at $3.42. The stock has already climbed 131% since the beginning of May due to anticipation for the ONT-380 data at ASCO.
ONT-380 was designed from the ground up to block HER2, a tumor-growing protein overexpressed in breast cancer, while leaving other, related tumor-causing proteins relatively untouched. Approved drugs like GlaxoSmithKline's (GSK) Tykerb and Puma's still-experimental neratinib inhibit HER2 plus another protein, which contributes to higher gastrointestinal and skin-related side effects.
The phase Ib study enrolled 32 patients with HER2-positive, metastatic breast cancer no longer responding to Roche's (RHHBY) Herceptin and Kadcyla. All the patients were treated with ONT-380 added to three different combination therapies: Xeloda, Herceptin or Xeloda plus Herceptin.