Shares in big pharma groups AstraZeneca and GlaxoSmithKline were under pressure this morning as brokers voiced concerns about future challenges.

Analysts at Goldman Sachs, the US investment bank, argued that both groups, with their sector peers, must become more active in developing new drugs as the challenge from generic versions of their current products increases.

The broker downgraded AstraZeneca to sell from neutral and cut its target price to £25.00 from £26.78, arguing that the stock was unlikely to outperform its peers as the wider market recovers and investors begin to assess the significant strategic longer-term challenges that face the company. Shares fell 114p to £25.28.

Goldman also has a "sell" rating on GlaxoSmithKline for similar reasons.

Glaxo, down 38.5p to £12.51.5, was hit after Exane BNP Paribas double downgraded the shares to "underperform" from "outperform", noting that the company had been supported recently by the appointment of a new chief executive but that it was entering a more risky period with 2009 likely to be heavily affected by generics. It added that there was little room for good surprises from near-term news flow on research.

Overall, the FTSE 100 fell 66.7 points to 5299.5, dragged down by a lower retail sector and continuing weakness in banks.

Retailers were hit by disappointing results from Argos owner Home Retail Group, down 15.75p to 226p, privately held department store John Lewis, and supermarket chain Wm Morrison, down 17.5p to 252.75p.

Banks continued to suffer from the fall out of losses at Lehman Brothers, the US investment bank, with Royal Bank of Scotland falling 6.75p to 233.25p and Barclays losing 11.25p to 335.25p.

The blue-chip index’s losses would have been greater, had it not been for a resurgent mining sector, which regained ground after weeks of being sold. Kazakhmys led the risers, up 36.5p to 861.5p, Xstrata gained 75p to £23.00 and Antofagasta added 17.5p to 505.5p.

BG Group was also among the index’s top risers, up 42p to £10.97, after its partner Petrobras said a new well has discovered between three and four billion barrels of oil equivalent in offshore Brazil.

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