The results from Merck's trial were almost identical to the results from the Bristol-Myers' (NYSE:BMY) trial which tested a combination of Yervoy and its experimental drug, nivolumab.
The objective response rate in the Merck trial across all doses was 41 percent, as evaluated by a blinded central review committee. Objective response rate includes all the patients who had either a complete or partial response.
In Bristol-Myers Squibb's presentation at ASCO in May, its drug nivolumab, in combination with Yervoy, achieved an objective response rate of 40 percent among the 53 patients treated.
Merck's MK-3475 trial has also showed an estimated overall survival rate of 81 percent at one year across all dosing groups. This is the first time overall survival data have been reported from the Phase 1b clinical trial which is still ongoing.
Merck's clinical trials
Merck is running a huge network of clinical trials to expand its immunotherapy effort.
MK-3475 has 10 clinical trials running with a total enrollment of 4,000 patients across a broad range of cancer types, including bladder, colorectal, gastric, head and neck, melanoma, non-small cell lung, triple negative breast and hematological malignancies. Additional trials are also planned.
MK-3475 was intravenously applied at a dose of 10 mg per kilogram of body weight every 2 or 3 weeks or 2 mg per kilogram every 3 weeks in patients who had received prior treatment with Yervoy as well as those who had not.
The confirmed response rate as evaluated by an independent radiologic review according to the Response Evaluation Criteria in Solid Tumors (RECIST) was 38 percent.
The highest confirmed response rate was observed in the group that received 10 mg per kilogram every 2 weeks.
Responses were durable in the majority of patients during a median follow-up of 11 months. 81 percent of the patients who had a response were still receiving treatment at the time of the analysis cut-off date in March 2013.
The overall median progression-free survival among the 135 patients was longer than 7 months.
The bottom line is that in patients with advanced melanoma, including those who had disease progression while receiving Yervoy, treatment with MK-3475 resulted in a high rate of sustained tumor regression.
Bristol-Myers isn't wasting any time extending the range of its own drug, nivolumab.
It has 6 late-stage studies underway, with FDA designated fast-track status in place for melanoma, lung cancer and kidney cancer. If the data continues to support the early results, Bristol-Myers will have a major new therapy in its portfolio.
The blockbuster Yervoy disables an immune system brake called CTLA-4, but it shrinks tumors in only about 10 percent of patients. Even though the effect in that small percentage of patients can be long-lasting and highly effective, that still leaves an urgent need for new drugs for patients with advanced melanoma.
Roche (OTCQX:RHHBY) targets PD-L1, which the company believes may be a safer approach. Early data from a small study showed that investigators could use the maximum dose safely, making this a strong candidate in mid-stage studies.
Roche's compound is known as MPDL3280A, developed by its Genentech subsidiary. Overall, tumors in 29 patients, or 21 percent, responded to the drug in an early trial.
In the future it may be possible to test tumors for the presence of PD-L1, and use the drugs mainly for those patients, where it is expected to work more effectively.
Roche is also in a hurry, it recently rushed the drug into Phase 3.
Bristol's nivolumab, and Merck's MK-3475 are antibodies that bind to PD-1, while Roche's drug binds to PD-L1. It is not clear yet which approach is better.
The key is the interaction between the PD-1 (programmed death) protein and PD-L1 (programmed death ligand) protein that allows cancer cells to escape and multiply.
By giving a patient the correct antibody protein to block either the PD-1 or PD-L1 from interacting, the immune system will destroy the cancer cells.
For decades scientists have been trying to understand why the body's immune system doesn't see cancer cells as the enemy and attack them.
Recent discoveries found that tumors create a sort of cloak of invisibility from the immune system. The new class of drugs lifts the cloaking device and allows the immune system to attack.
"You're setting up a fair fight" with the disease, said Nils Lonberg, a senior vice president at Bristol-Myers, in an interview. "The immune system is just as adaptable as the cancer."
It is not clear yet how many types of tumors the drugs will work for. All the companies are targeting melanoma because there is evidence that it is sometimes controlled spontaneously by the immune system. The companies also have data for lung and kidney cancer. Roche's study showed some effect in colorectal and head and neck cancer as well.
Some immunotherapy agents hold particular promise in being paired with drugs that specifically target genetic mutations driving the tumors. Since immunotherapy agents are treating the immune system, and not the cancer itself, this sort of approach should work against different kinds of cancer.
Even companies that don't have any PD-1 or PD-L1 drugs in their pipeline, like Pfizer, are interested studying them in combination with their own targeted cancer drugs.
For PD-1 and PD-L1, the most important interaction is at the tumor site as opposed to the broader impact across the immune system, which is what Yervoy does by targeting CTLA-4.
In the third quarter Merck's pharmaceutical sales declined 4 percent to $9.5 billion.
Sales of Singulair, Maxalt, Temodar and Cozaar declined following loss of market exclusivity. The losses were partially offset by growth in Remicade, Gardasil vaccine, Simponi and Isentress.
Singulair, a once-daily oral medicine for the chronic treatment of asthma and the relief of symptoms of allergic rhinitis, declined 53 percent in sales to $280 million in the third quarter. The patents for Singulair expired in the U.S. in 2012 and in major European markets in early 2013. A rapid fall in sales followed the patent expiry.
Combined sales of Remicade and Simponi, treatments for inflammatory diseases, increased 22 percent to $700 million in the third quarter.
Global sales of the combined diabetes franchise of Januvia and Janumet decreased 1 percent to $1.4 billion.
Sales of Zetia and Vytorin (a combination of Zetia and Zocor), medicines for lowering LDL cholesterol, decreased 1 percent to $1.1 billion in the third quarter. The decrease reflects lower sales of Vytorin, partially offset by growth of Zetia in the U.S.
Merck's sales of Gardasil, a vaccine to help prevent diseases caused by four types of human papillomavirus, were $665 million, an increase of 15 percent for the quarter. The increase was driven by continued strong uptake of its use in males in the U.S., and higher public sector sales of $60 million.
The company's gross margin declined to 62.8 percent in the third quarter of 2013 from 64.0 percent for the third quarter of 2012, reflecting primarily the impact of patent expiries.
Merck has lowered its non-GAAP earnings forecast to a range of $3.48 - $3.52 per share.
The company has increased its quarterly dividend to $0.44, up $0.01 from $0.43 per share paid last quarter. Payment will be made on January 8, 2014, to stockholders of record on December 16, 2013.
Over the past few years Merck has gained a reputation of having a hugely expensive research program coupled with a growing roster of setbacks in the clinic.
There is an air of urgency and excitement around MK-3475, which is demonstrated by the sheer size of the clinical trials, unprecedented for the company. Merck badly needs a winner from its pipeline and MK-3475 has a clear promise to become one.
Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours. I wrote this article myself, and it expresses my own opinions. I am not receiving compensation for it (other than from Seeking Alpha). I have no business relationship with any company whose stock is mentioned in this article.