TRENTON, N.J. (AP) -- Experimental drugs that help the immune system detect otherwise-invisible cancer cells shrank tumors and extended the lives of patients with advanced melanoma, according to early research some analysts are hailing as an approach that could become the future gold standard of care for multiple cancer types.
The data presented Sunday, on drugs being developed by Merck & Co., Bristol-Myers Squibb Inc. and The Roche Group, were the talk of a huge five-day conference of cancer specialists in Chicago, hosted by the American Society of Clinical Oncology.
The Bristol-Myers and Merck drugs for advanced melanoma — skin cancer that has spread or cannot be removed by surgery — are in a new class called PD-1 therapies, short for programmed death.
The antibody drugs enable the patient's immune system to identify tumor cells that otherwise would evade detection because they have the equivalent of an invisibility cloak. Once the cancer cells are "uncloaked," powerful immune system cells called T cells can target and destroy the cancer cells.
The promising results, while in small patient studies, pumped up shares of Merck and Bristol-Myers to multi-year highs on Monday, as several analysts issued encouraging reports stating that the drugs seem very effective and had relatively minor side effects, mostly diarrhea, fatigue, itching and rashes. A few patients developed lung inflammation.
The reports also noted that both drugmakers already are studying their drugs in a few other types of cancer, and these drugs and similar ones might work against additional cancer types — blood cancers as well as solid tumors.
Both drugs are part of a promising new area of cancer research called immuno-oncology, in which drugs stimulate a patient's immune system to fight their cancer, rather than indiscriminantly killing both cancer and healthy cells, the way chemotherapy does. Such targeted approaches could limit some of the worst side effects of cancer treatment, such as vomiting and hair loss.
A few analysts wrote in reports on Monday that combinations of two or more such immune drugs, or one of them with another type of cancer drug, could well be the future of cancer therapy and might shorten its duration.
Melanoma is the deadliest skin cancer and is becoming more common in young people. More than 80 percent of skin cancer deaths are caused by advanced melanoma, and an estimated 9,180 people in the U.S. died from it last year, according to the American Cancer Society.
The drug being developed by Merck, of Whitehouse Station, N.J., is called lambrolizumab. It was tested at three different doses in a total of 135 patients. On average, 38 percent of them responded to the treatment, meaning their tumors shrank at least somewhat. In those getting the highest dose, 52 percent responded. In some patients, the improvement lasted more than eight months and was continuing when the data reported Sunday were collected.
UBS Securities analyst Marc Goodman wrote that Merck's strong results from its study and its program testing its drug against lung, breast, bladder and other cancers "should enable it to be very competitive in this potentially large and exciting space."
New York-based Bristol-Myers presented an early-stage study of its nivolumab. The 86 patients tested also were treated either at the same time or sequentially with the company's melanoma medicine Yervoy, a drug launched two years ago that was the first shown to prolong the lives of patients with advanced skin cancer. In one of the dose combinations tested, 53 percent had their tumors shrink by at least 80 percent and in three of those, the tumor disappeared.
"Bristol-Myers stole the show," Barclays Capital analyst Tony Butler wrote to investors. "Most startling was the estimated one-year overall survival rate of 82 percent."
Some patients in Bristol-Myers' study had their tumors shrink even after they stopped taking the drug, indicating its effects endure, at least for a while.
Needing a shorter treatment time would be great for patients, but less so for Bristol-Myers since the less time a patient needs to stay on the drug, the less money the company would make.
Still, analysts estimated Bristol-Myers' drug could eventually generate well over $6 billion a year in revenue just from treating advanced melanoma, and more if it is successful in treating other cancers. That could make it one of the most lucrative blockbusters — drugs generating more than $1 billion in annual sales — that the pharmaceutical industry has seen.
That's partly because the PD-1 therapies, if approved, are likely to be very pricey, as they are biologic medicines, "manufactured" in living cells rather than by mixing chemicals together.
Switzerland's Roche also presented data at the conference on several studies testing its own "engineered antibody" drug, MPDL3280A, against various cancer types. A study in patients with metastatic melanoma found 29 percent responded to the drug, while in three other cancer studies 13 percent to 22 percent of study participants responded to the medicine.
Like the Merck and Bristol-Myers drugs, Roche's drug is meant to give the immune system the upper hand over cancer cells by making them more visible.
MPDL3280A works by binding to a protein, or receptor, called PD-L1 on cancer cells. The Merck and Bristol-Myers antibody drugs instead bind to a receptor on the T cells, activating them and enabling them to see cancer cells.
In Monday trading, Bristol-Myers shares closed up $1.58, or 3.4 percent, at $47.59, after peaking during the session at $49.57, its highest point in 11 years.
Merck shares also saw an unusually big jump during the trading day, rising as high as $49.36, a point last seen five years ago, before paring back a bit to close up $1.75, or 3.8 percent, at $48.45.
Follow Linda A. Johnson at http://twitter.comLindaJ_onPharma .