Nov 2 (Reuters) - Amgen Inc on Tuesday reported a 4% increase in third-quarter revenue as the impact of the COVID-19 pandemic on drug prescriptions began to ease, but said prices for some of its drugs remained under pressure from lower-cost competition.

The biotechnology company's adjusted earnings for the quarter, helped by share repurchases, reached $4.69 per share, beating the $4.27 per share forecast by Wall Street analysts, as compiled by Refinitiv.

Net earnings per share fell 3% to $3.31 driven by a $400 million licensing-related expense from Amgen's collaboration with Japan's Kyowa Kirin Co Ltd.

Revenue for the quarter totaled $6.7 billion, up 4% from $6.4 billion a year earlier, and in line with analyst expectations.

Amgen said sales volumes for the quarter rose 8%, but net selling prices fell 7% as competition, including from cheaper generics and biosimilars, pushed down prices for its arthritis, migraine and infection-fighting drugs.

Sales of arthritis drug Enbrel fell 3% from year earlier to $1.29 billion. Sales of newer cancer drug Lumakras totaled $36 million for the quarter, ahead of analyst estimates of $28 million.

For the full year, Amgen raised its estimate for adjusted earnings per share to a range of $16.50 to $17.10 from a previous $16.00 to $17.00 per share, but lowered the top end of its revenue forecast to $26.2 billion from a previous $26.6 billion. (Reporting By Deena Beasley; Editing by David Gregorio)