Friday, 29 March, 2024
HomeWeekly RoundupUS approves Keytruda Tx based on specific genetic traits

US approves Keytruda Tx based on specific genetic traits

Merck & Co's immunotherapy Keytruda has become the first cancer drug approved by the US Food and Drug Administration based on a patients' specific genetic traits, regardless of where in the body the disease originated. According to a Scientific American report, the approval marks a major step in so-called precision medicine, where genetic biomarkers may determine the course of therapy rather than the type of cancer. The hope is that advanced genetic information will one day be able to identify which patients are most likely to benefit from a specific treatment.

"Until now, the FDA has approved cancer treatments based on where in the body the cancer started – for example, lung or breast cancers," said Richard Pazdur, head of oncology products for the FDA's Centre for Drug Evaluation and Research.

The accelerated approval was for solid tumour cancers not eligible for surgery or that have spread in patients identified as having a biomarker called microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). Tumours with those traits are most common in colorectal, endometrial and gastrointestinal cancers, but may also appear in cancers of the breast, prostate, bladder, pancreas, thyroid gland and others.

Dr Drew Pardoll, director of the Johns Hopkins Bloomberg-Kimmel Institute that designed and led the trial that led to the historic approval, called it "a marriage of cancer genetics and cancer immunology."

Patients whose tumours are laden with the genetic defect have an abundance of abnormal proteins that look more foreign to immune cells, triggering them to search out and destroy the cancer cells.

The report says Keytruda belongs to a new class of drugs called PD-1 or PD-L1 inhibitors that block a mechanism tumours use to evade detection from cancer-fighting cells. There are now five such drugs available for a variety of cancers. "This was one of those eureka trials where it didn't take a lot of patients to see this was going to be something major," Pardoll is quoted in the report as saying. He said about 4% of advanced cancers, or 15,000 to 20,000 cases each year in the US, carry the genetic traits addressed in the approval.

The approval covers children and adults whose cancer has progressed despite prior treatment and those who have no satisfactory alternative treatment options, including patients whose colorectal cancer has progressed following chemotherapy.

The report says the FDA grants accelerated approvals to drugs for serious conditions with unmet medical needs if the treatment appears to have effects deemed reasonably likely to predict a clinical benefit. Merck must still conduct studies to confirm the anticipated benefit.

The approval further solidifies Merck's leading position in the burgeoning field of treatments that help the immune system fight cancer, a mantle it seized last year when Keytruda extended survival as an initial treatment for advanced non-small cell lung cancer (NSCLC).

Keytruda was previously approved to treat advanced melanoma, advanced NSCLC, head and neck cancers and classical Hodgkin lymphoma. Last week it won US approval for bladder cancer and is awaiting an FDA decision for gastric cancer.

[link url="https://www.scientificamerican.com/article/fda-clears-first-cancer-drug-based-on-genetics-of-disease-not-tumor-location/"]Scientific American report[/link]

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