Rare mutation tests restricted by lack of insurance coverage
Precision cancer treatments have been held back by US health insurance coverage. Loxo Oncology has developed a tumour-agnostic drug that treats cancers with a gene mutation called TRK. The mutation is very rare, therefore patients need expensive genetic tests to identify it, which are not often covered by insurance. Robert Doebele, an oncologist and TRK researcher at Colorado State University, said it was often difficult to convince doctors to test for such a rare mutation that may only affect 1% of patients, as many were concerned those in their care would get a $5,000 bill.
The company’s drug, which could be on the market as early as next year, treats cancers with a mutation in a gene called TRK. That could be welcome news for patients desperate for a precision strike on their tumors. But the mutation is so rare—and gene testing is still uncommon enough—that the question is how many patients who need it will get the drug.

Drugs like Loxo’s gained attention last month, when the U.S. Food and Drug Administration, for the first time, gave a green light for doctors to prescribe another cancer drug, Keytruda, based on specific genetic features of cancers rather where in the body where the disease originated.

The drug being developed by Connecticut-based Loxo could be the next such targeted medicine in line for possible FDA approval (see “Slow Progress to Better Medicine”).

But to prescribe such drugs, doctors will have to know the genetic makeup of a tumor—and so far in the U.S. only 12 percent of late stage metastatic cancer patients are getting tests that screen broadly for genetic mutations, according to Cambridge, Massachusetts-based genetic testing company Foundation Medicine.

Mutations in TRK, a gene that provides instructions for making a protein necessary for the development and survival of certain nerve cells, was first discovered as the culprit behind some colon cancers in 1982. Scientists wouldn’t find out until 2013 and 2014 that TRK mutations occur in other types of cancer, including of the breast, lung, and skin.

In 2015, Loxo began the first clinical trial for a cancer drug targeting TRK in 17 different types of tumors. “It doesn’t matter what the context is, the drug seems to be working in the same way because the biology is comparable,” says Loxo CEO Josh Bilenker.

The company started treating patients in spring 2015 after partner medical centers used genetic testing to identify a handful of people with TRK mutations. It took 15 types of tests and two years to enroll 55 patients.

This past weekend at the American Society of Clinical Oncology annual meeting in Chicago, Loxo announced striking results—though in a small number of patients—for its lead drug, larotrectinib, which is designed to turn off the signaling pathway that allows TRK fusion cancers to grow. In 50 adults and children with more than a dozen different types of cancer, the drug shrank tumors in 38 patients, or 76 percent. In 30 of those patients still on the drug, their tumor growth halted completely and no new tumors formed after 12 months of treatment. No patients stopped taking the drug due to side effects.