Merck & Co. Inc.'s Keytruda and Bristol-Myers Squibb Co.'s Opdivo are locked in a five-year battle for dominance of the cancer market.

At the 2019 Annual Meeting of the American Society of Clinical Oncology that ran from May 31 to June 4, the two pharma giants presented the latest research from their ongoing efforts to discover what their respective drugs can do in the cancer sector.

Both drugs have racked up U.S. Food and Drug Administration nods since their original approvals in 2014. Keytruda holds the lead with approval in the U.S. for 19 separate indications — including expanded and combination treatments — while Opdivo has 15.

Keytruda's drastic lead has come about only recently: Since August 2018, Keytruda has picked up seven new uses in cancer, while Opdivo has been stagnant on the regulatory front.

Both immuno-oncology drugs work by triggering the immune system to attack cancer cells by inhibiting the PD-1 arm of healthy cells, which in turn prevents the corresponding PD-L1 arm of cancer cells from latching to the healthy cells. They are called immune checkpoint inhibitors.

Lung cancer has been a mainstay for both treatments, with Keytruda holding the edge, but at ASCO, a wide array of clinical trial results were highlighted. Our reporter previews the stakes for both pharma giants.

Story: Merck and Bristol-Myers face off at ASCO meeting

Child enrollment in Medicaid programs sees largest drop since 2000, study finds

Child enrollment in Medicaid programs dropped by 828,129 in 2018, the highest year-over-year decline in enrollment since at least 2000, according to a new study from Georgetown University's Center for Children and Families.

Technology disruption in healthcare to put more power in consumer's hands

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Physician burnout costing US economy $4.6B annually, study finds

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Novartis' gene therapy for rare infant disease to compete with Biogen's Spinraza

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BioMarin's gene therapy for hemophilia reduced bleeding by 96% over 3 years

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Mallinckrodt to spin off specialty generics unit, rename specialty brands group

Mallinckrodt PLC is spinning off its specialty generics and active pharmaceutical ingredients business to its shareholders.

Essential Healthcare is a weekly collection of critical developments across the pharmaceutical, biotechnology, healthcare provider, healthcare technology and medical equipment industries that draws on exclusive analysis and value-added content from the Healthcare News team at S&P Global Market Intelligence. Subscribe now to get Essential Healthcare delivered to your inbox every week.