Merck & Co said it would fast track its plans to submit new drugs for hepatitis C and lung cancer for regulatory approval.
The drugmaker is trying to close the gap with competitors in the two lucrative segments.
Gilead Sciences Inc's hepatitis C drug, Sovaldi — priced at $84,000 per course — notched up sales of $2.8 billion in the company's latest quarter.
Last month, the U.S. Food and Drug Administration approved AbbVie Inc's all-oral hepatitis C treatment, priced lower than Gilead's drugs.
Merck said it planned to file an application with the FDA in the first half of the year for marketing approval for grazoprevir/elbasvir, a new two-drug, single-pill combination to treat hepatitis C.
The company had said in November that it planned to submit the new drug application sometime in 2015.
Merck also said it would file an application midyear for expanding the use of its new cancer immunotherapy Keytruda to include the treatment of non-small-cell lung cancer, the most common form of the deadly disease.
Merck's plan to speed up the drug submissions was first reported by the Wall Street Journal.
Keytruda belongs to a new class of drugs, called PD-1 inhibitors, that have generated great enthusiasm in the medical community.
They work by blocking a mechanism tumors use to camouflage themselves from the immune system, allowing it to recognize and attack the cancer.
The FDA approved Keytruda last year to treat advanced melanoma, the deadliest form of skin cancer, making it the first drug from the PD-1 class to reach the U.S. market.
Rival drugmaker Bristol-Myers Squibb Co said on Sunday an independent data monitoring committee concluded that a late-stage study evaluating its skin-cancer drug Opdivo in previously treated patients with advanced, squamous cell non-small-cell lung cancer met its main goal.
Merck shares, which have gained 10 percent in the first six trading days of 2015, rose as much as 1.5 percent to touch a more than 13-year high at $63.50 on Monday on the New York Stock Exchange.
(Reporting by Supriya Kurane and Ankur Banerjee in Bengaluru; Editing by Gopakumar Warrier)