Merck and Roche prep breast cancer data for promising immunotherapy drugs

As fervor surrounding a new class of cancer drugs builds, drug giants Merck ($MRK) and Roche ($RHHBY) are set to roll out new data for their opposing immunotherapy drugs for breast cancer by the end of the year.

Along with AstraZeneca ($AZN) and Bristol-Myers ($BMY), Merck is developing a drug designed to block a molecule called PD-1--short for programmed cell death protein 1--spurring the immune system into action to attack the tumor cells. Left unchecked, this switch allows cancerous cells to pass undetected. Meanwhile, Roche is testing its PDL-1 drug, designed to inhibit the interaction of programmed death-ligand 1 with PD-1.

Merck and Roche are hoping to widen this novel approach to treat advanced triple-negative breast cancer, which is notoriously impervious to some of the most effective therapies available for breast cancer, like hormone therapy and drugs that target HER2 receptors. The New Jersey-based drugmaker and Swiss company will present early clinical results at the San Antonio Breast Cancer Symposium in December, according to Reuters.

Roche's drug, MPDL3280A, has already posted encouraging results in bladder, lung and skin cancers though it's not yet approved to treat any indications. Meanwhile, Merck is studying how triple-negative breast cancer patients fair with its PD-1 drug Keyruda, which won approval for melanoma and has shown promise in stomach and other cancers.

Bristol-Myers is also moving in on this target, with its August announcement that it will begin a Phase I breast cancer trial of its PD-1 drug nivolumab alongside Celgene ($CELG) Abraxane. Bristol-Myers' drug, which it developed with partner Ono Pharmaceutical, scored a landmark approval from Japan's drug regulator in July to treat melanoma.

Bristol was also the first to submit a global regulatory nod for its PD-1 drug in lung cancer, a particularly lucrative indication, and seems well positioned to grab a major share of a new market expected to reach nearly $35 billion a year.

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