Yesterday Merck (MRK) announced that it had obtained positive phase 3 results in patients with Melanoma using its drug known as Keytruda -- pembrolizumab. The trial for testing Keytruda was known as the KEYNOTE-006 study which recruited up to 834 patients. The patients recruited in the trial were people who had stage III or stage IV advanced melanoma and had only received one prior systemic therapy before taking Keytruda. 

Each clinical trial patients were randomized into one of the three dose groups:

1. Keytruda 10 mg/kg every 3-weeks
2. Keytruda 10 mg/kg every 2-weeks
3. 4 cycles of ipilimumab 3 mg/kg every 3-weeks

Keytruda is a monoclonal antibody produced by Merck to block the interaction of PD-1 -- programmed cell death receptor-1  -- and its ligands PD-1 / PD-2 in cancer cells. The current standard of care for Melanoma patients is Ipilimumab, marketed as Yervoy, produced by Bristol-Myers Squibb (BMY) as a front-line therapy for advanced melanoma patients.  

Merck reported that Keytruda met on both co-primary endpoints of the trial. The first primary endpoint was progression-free survival, which is how long a patient goes in the treatment without the cancer getting progressively worse. The other primary endpoint was looking at the overall survival of patients. Overall survival is an average of how many months the patients survive in the trial while on the treatment regimen. Keytruda showed both better progression-free survival and better overall survival against Yervoy -- placebo in the trial. The full trial results will be shown this April 2015 at the American Association of Cancer Research (AACR) annual meeting being held in Philadelphia. 

Despite this positive news announcement yesterday, shares of Merck closed just about flat for the trading day Tuesday.  In addition to positive trial results Merck also announced Tuesday that its board has authorized an additional $10 billion in share repurchases. One thing to note  is that these share repurchases will happen on the open market at random times. After a brief spike this morning, MRK stock closed down 0.65%.

Merck is testing its Keytruda drug in more than 30 different cancer indications either alone or in combination with other cancer drug therapies. Merck may be able to add more value to shareholders as other cancer trials continue to show similar efficacy results seen in this Melanoma trial.