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FDA Clears Mersana to Restart Cancer Drug Trial With New Safeguards

Xconomy Boston — 

The FDA has cleared Mersana Therapeutics to resume enrolling patients in a study of an experimental cancer drug now that the Cambridge, MA, company is taking new precautions to protect patients from potential harm.

The company says the FDA lifted a “partial clinical hold” on the Mersana (NASDAQ: MRSN) drug XMT-1522, a move that had temporarily stopped the biotech from recruiting patients for a Phase 1 trial. The agency slapped a hold on Mersana after the death of a patient in the study was deemed “possibly drug related” by an investigator.

XMT-1522 is what’s known as an antibody-drug conjugate (ADC), a type of cancer drug that links a toxic chemical to a tumor-targeting antibody. ADCs are meant to provide a more targeted strike on cancer and spare healthy tissue in the process. But while there are a couple of approved ADCs, including the breast cancer drug ado-trastuzumab emtansine (Kadcyla), they have yet to fulfill their early promise. Several have disappointed in clinical testing.

Mersana has been developing XMT-1522 to go after tumors that express the HER2 protein. It’s been enrolling patients in a Phase 1 study who have either breast, stomach, or lung cancer, hoping to show that it can prove effective across different cancer types and even in people whose tumors express low levels of HER2. But in trying to find the right dose of XMT-1522 to take into later tests, Mersana reported in July that a patient died while taking one of the higher doses.

Mersana says it will now monitor patients more closely—though it didn’t provide specifics—and won’t test the drug in patients with liver damage. It will also test new dosing schemes, such as administering the drug once every four weeks. Mersana is immediately implementing the same changes to another drug program, XMT-1536—being tested in ovarian and lung cancer patients—as well. The FDA hadn’t stopped any tests of XMT-1536.

Mersana shares fell 19 percent in midday trading. XMT-1522 is part of a partnership with Takeda.

Here’s more on Mersana and ADCs.

[Top image of triple negative breast cancer by Kevin Janes of the University of Virginia, used under public domain rules courtesy of the National Cancer Institute.]