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Keytruda gets priority FDA review for biomarker-positive tumours

Merck & Co’s immuno-oncology drug used for colorectal cancer

Merck & Co US headquartersMerck & Co says it will get a speedy FDA review for its immuno-oncology drug Keytruda for use in patients whose tumours carry a particular biomarker.

Merck - known as MSD outside North America - has sought US approval for PD-1 inhibitor Keytruda (pembrolizumab) as a second-line treatment for patients with advanced microsatellite instability-high (MSI-H) cancer, which is thought to predict whether a cancer patient will respond to treatment with an immunotherapy.

At the moment the PD-L1 protein that binds to the PD-1 receptor is most commonly used as a biomarker to predict whether drugs like Keytruda will be effective, but is known to be an imperfect assessment. Some tumours with high PD-L1 levels stubbornly resist treatment, while others with low levels respond well.

Keytruda was awarded breakthrough status by the FDA last year for advanced colorectal patients with high MSI levels, and recently picked up another broader breakthrough designation for non-colorectal cancer patients. MSI occurs in approximately 15% of all colorectal cancers and is generally associated with a reduced rate of tumour recurrence and more favourable survival - provided it is identified and treated at an early stage.

Merck notes that microsatellites are short, repetitive sequences of DNA found throughout the genome, and MSI is caused by a deficiency in cells' ability to repair errors in DNA sequences. The biomarker is already being used to select patients for treatment in some clinics in the US.

In fact, recently-updated guidelines from the National Comprehensive Cancer Network (NCCN) recommend that MSI testing be done in all patients with newly-diagnosed colorectal cancer.

Clinical data suggest that checkpoint inhibitors like Keytruda can have a dramatic impact on MSI-positive colorectal cancer if identified early, much greater than traditional chemotherapy, although at the moment there is no approved PD-1 or PD-L1 inhibitor for this form of cancer. 

Merck's immuno-oncology arch-rival Bristol-Myers Squibb (BMS) reported data earlier this year showing that its PD-1 inhibitor Opdivo was also effective in MSI-H colorectal cancer, both alone and in combination with its CTLA4 inhibitor Yervoy (ipilimumab).

Merck says its FDA application is seeking a green light to use Keytruda at a fixed dose of 200mg every three weeks in MSI-H cancer, and it is now pitching at a decision by the regulator by 8 March 2017.

"We believe that patients whose tumours harbour DNA repair defects may be especially responsive to Keytruda," said the company's head of R&D Dr Roger Perlmutter. "We look forward to working with the FDA to bring this important new therapy to these very challenging treatment situations."

Article by
Phil Taylor

29th November 2016

From: Research, Regulatory



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