At least 19 immune therapies are being tested in 122 clinical trials, according to Leerink Partners, an investment bank specializing in healthcare. Many won’t pan out but there have been exciting early results, particularly in a new class called checkpoint blockers. Merck’s pembrolizumab has shown promise fighting advanced melanoma, a skin cancer that typically kills most of its victims within a year of diagnosis. In a study of 411 patients who took the drug, 62 percent were alive 18 months after starting treatment. Nivolumab, a drug being developed by Bristol-Myers Squibb, also boosted long-term survival in melanoma patients. Of those who took it with another immunity-enhancing medicine, 88 percent were alive after two years. Nivolumab and pembrolizumab target the protein PD-1, which acts as a switch that shuts off cells that attack cancers. Other immune therapies work by supercharging the body’s cancer-fighting T-cells. Ultimately, the most successful treatments may be combinations of the drugs, and it’s possible that immune therapies will be part of every cancer regimen.
Science first stumbled across the human body’s natural cancer defenses in the 19th century, when doctors noticed tumors shrinking after patients developed infections. Experiments in stimulating antibodies to fight cancer weren’t promising, so radiation, then chemotherapy, became the favored treatments despite sickening side effects. An early immune-therapy drug, Interleukin-2, was approved in 1992 and slowed growth in melanomas. But the drug produced aches, nausea, diarrhea and even heart attacks and strokes, so patients had to be kept in the hospital for treatment. As scientists learned more about the human genome, medicines were developed that could target parts of the body without damaging the rest. The current fascination with immune therapies was triggered in 2012, when Bristol-Myers presented data that nivolumab could treat patients with lung and kidney cancer, as well as melanoma.
The therapies haven’t yet been proven to work against some common cancers like those of the lung. They don’t work in every patient and they’ve only been tested for advanced forms of cancer, so it’s possible they won’t be as effective if used in earlier stages. Some diseases, like prostate and pancreatic cancers, have proven resistant. Costs may also be an obstacle to widespread use. For Yervoy, a melanoma immune therapy approved in 2011, Bristol-Myers charges $30,000 per injection in the U.S. – a total treatment costs $120,000 and the drug has serious side effects. There’s also the lesson of history: Cures for cancer have been predicted before, only to disappoint. Among notable examples are the angiogenesis drugs of the late 1990s, which some experts predicted would end cancer in two years. Some of those drugs, which restrict blood flow to tumors, are in use today but the cure for cancer remains elusive.
The Reference Shelf
- The New Yorker published a history of immune therapy in 2012 by Jerome Groopman, a Harvard Medical School researcher.
- The American Cancer Society has a primer on immune therapy.
- Bloomberg News reported in June about recent advances.
- Dr. Siddhartha Mukherjee examined the history of cancer and its treatment in a Pulitzer Prize-winning 2011 “biography,” “Emperor of All Maladies.”