GlaxoSmithKline is assessing final bids for a clutch of its non-prescription drugs, keeping the process on track for the selection of a buyer by the end of the year, people familiar with the matter said on Monday.

The final, second-round bids are in. The deadline was the end of last week, said one source.

Private equity firms have dominated the process, with Bain Capital and Blackstone , which has partnered with Prestige Brands

, seen as the two front-runners.

The private equity bidders are interested in acquiring the portfolio of products up for sale, while a handful of trade buyers have been focused on picking up selected brands.

A spokesman for the British drugmaker declined to comment on latest developments in the auction, which is being handled by Goldman Sachs.

However, GSK Chief Executive Andrew Witty said last month he aimed to conclude the bidding process by the end of December, leaving open the possibility that final completion might occur in the new year.

Reuters reported at the time that GSK aimed to receive second-round bids by mid-November.

Analysts initially said the over-the-counter (OTC) products might raise between 1.5 billion and 2 billion pounds ($2.4-3.2 billion), or three to four times sales -- a cash windfall that GSK could use to underpin share repurchases in 2012.

But some believe the price will be pressured by uncertainty over prospects for diet pill Alli, which is included in the mix, as well as the tough funding environment facing private equity bidders.

GSK put a book value of 700 million pounds on the non-core OTC products it aims to sell at its third-quarter results. In addition to Alli, the products up for sale also include painkillers and vitamin supplements, all sold primarily in Europe and the United States.

Trade players including German groups Bayer , Sanofi and Boehringer Ingelheim have shown interest in specific parts of the portfolio, rather than buying the products as a block, which is the option GSK would prefer.

Despite the divestment, consumer healthcare will still remain a priority area for GSK. The company aims to focus its portfolio on top brands in Western markets and concentrate heavily on fast-growing opportunities in emerging markets.

(Reporting by Ben Hirschler; Editing by Jon Loades-Carter)