(Reuters) - Merck & Co's MRK.N blockbuster drug Keytruda helped previously untreated lung cancer patients live longer in a late-stage trial, potentially cementing its position as the dominant player in the lucrative lung cancer market.

Merck's cancer drug Keytruda. REUTERS/via Merck

Shares of the drugmaker were up 3.1 percent at $55.07.

Merck is already considered the frontrunner in the space and Keytruda is expected to earn peak sales of over $10 billion in 2023, according to Credit Suisse.

Keytruda is already approved in the U.S. to treat patients with non-small cell lung cancer (NSCLC) who have not received prior therapies and whose tumors show PD-L1 protein levels of 50 percent or greater.

If the company can show that the new data benefits patients whose PD-L1 expression is between 1 and 49 percent, it would expand Keytruda's market and raise the competitive benchmark for rivals Bristol-Myers Squibb BMY.N and AstraZeneca Plc AZN.L, BMO Capital Markets analyst Alex Arfaei said.

An independent data monitoring committee determined the trial, which tested Keytruda as a monotherapy to treat NSCLC, extended the lives of patients significantly compared to chemotherapy.

Additional data from Merck, as well as results from trials of competitors, could eventually determine which companies will snatch the largest slice of the pie for the lung cancer market.

“I think the market still believes that there could be other players in the lung cancer market, which would combat overall sales of Keytruda in this setting,” Guggenheim Securities analyst Tony Butler told Reuters.

“Because we don’t know the full data set we don’t know the survival benefit here.”

Based on a recommendation from the committee, the trial will continue to evaluate a secondary goal on whether the treatment can delay the disease from progressing.

“While it is still unclear whether Keytruda and (Bristol-Myers’) Opdivo are truly different in some way, it is crystal clear that Merck has done a much better job designing trials and developing their drug. This will solidify their lead,” said Brad Loncar, chief executive officer of Loncar Investments, which runs the Loncar Cancer Immunotherapy ETF.

Keytruda, which is approved to treat several other forms of cancer including skin and blood cancer, racked up $3.81 billion in revenue in 2017.

Lung cancer is the second most common cancer and is expected to kill over 154,000 people this year, the American Cancer Society says. NSCLC accounts for about 85 percent of all lung cancer cases, Merck said.

Shares of Bristol-Myers fell 2.3 percent to $59.43.