FDA approves new kind of cancer treatment

On May 23, the US Food and Drug Administration (FDA) granted accelerated approval to pembrolizumab, made by Merck and marketed as Keytruda, for adults and children without remaining treatment alternatives and with metastatic solid tumors identified with a biomarker called microsatellite instability-high (MSI-H) or mismatch fix deficient (dMMR).

"Nearly 100,000 people are living with gastric cancer in the United States, yet little progress has been made in bringing forward new treatment options to these patients for whom chemotherapy has always been the standard of care", Roger D. Dansey, MD, senior vice president and therapeutic area head for oncology late-stage development at Merck Research Laboratories, said in a company-issued press release.

The approval of this treatment is a big deal in the cancer community, Dr. Richard Pazdur said on behalf of the FDA.

The accelerated approved was based on tumor response rate and durability of response, with continued approval contingent on confirmatory clinical trials.

The genetic abnormalities common to these tumors affect the proper fix of DNA inside cells.

The FDA says those are typically found in colorectal, endometrial and gastrointestinal cancers, but bladder, breast and thyroid cancers can have the markers as well. Patients must also have metastatic or inoperable forms of those cancers, and have shown disease progression after previously receiving another treatment. The drug "may help the body's immune system fight the cancer cells" but the FDA doesn't specify how.

Keytruda works by targeting the cellular pathway called PD-1 or PD-L1, which are proteins located on the body's immune cells and certain cancer cells.

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Keytruda has additional approved indications in melanoma, lung cancer, head and neck cancer, Hodgkin lymphoma and urothelial carcinoma. Merck must still conduct studies to confirm the anticipated benefit. The ORR was 36 percent in patients with CRC and 46 percent in patients with other tumor types. Ninety patients had colorectal cancer (CRC) and the remaining 59 patients had 1 of 14 other tumor types. About 5 percent of people with spreading colorectal cancer have this biomarker. Among responders, 78% had responses of 6 months or greater.

Common adverse events due to pembrolizumab included constipation, cough, decreased appetite, diarrhea, dyspnea, fatigue, musculoskeletal pain, nausea, pruritus, pyrexia, and rash. Complications or death related to allogeneic hematopoietic stem cell transplantation after using pembrolizumab have occurred.

Patients who experience severe or life-threatening infusion-related reactions should stop taking Keytruda. And women who are pregnant or breastfeeding shouldn't take Keytruda because it could harm a developing fetus or newborn.

IHC identified dMMR cancer in 47 patients, MSI-H was identified by PCR in 60 patients, and 42 patients were identified with both tests.

Meanwhile, the regulators also granted a priority review to Merck's application to market Keytruda for the treatment of recurrent or advanced gastric or gastro-oesophageal junction adenocarcinoma.

It's not flawless, and more research has to be done, but the approval is a landmark because it's the first time a cancer treatment that is not site- or tissue-specific has received the agency's approval.

The FDA, an agency within the U.S. Department of Health and Human Services, protects the public health by assuring the safety, effectiveness, and security of human and veterinary drugs, vaccines and other biological products for human use, and medical devices.

  • Myrtle Hill