Should you buy Shire plc, Marks and Spencer Group plc and Amec Foster Wheeler plc following today's news?

Medical play Shire(LSE: SHP) furnished the market with positive regulatory news on Tuesday, news that sent the stock to fresh nine-month highs earlier today.

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Shire announced that the US Food and Drug Administration had signed off on its Xiidra product, which is used to treat dry eye disease in adults.

Shire notes that "Xiidra is thefirstprescription eye drop FDA-approved to treat both the signs and symptoms of dry eye disease," a situation that could make the drug an explosive sales driver. The pharma ace estimates that around 16m Americans suffer from dry eye disease.

The drug is now scheduled for rollout in the US during the third quarter, Shire added.

Safe-haven buying in the fallout of June's Brexit vote has given medical plays like Shire a huge shot in the arm. And I expect the Dublin-based firm to maintain its upward momentum as its packed product pipeline delivers the goods.

And I reckon a forward P/E rating of 16.1 times still offers plenty of upside for investors thinking of piling-in to Shire.

Contracts claimed

Engineering giant Amec Foster Wheeler(LSE: AMFW) also published positive trading news on Tuesday.

The firm announced that it had secured two long-term contracts with Repsol Sinopec Resources UK in the North Sea. The contracts will see Amec provide "maintenance and construction labour and engineering support services."

Still, I believe oilfield service providers like Amec are likely to remain under severe pressure as an environment of weak crude prices pressures capex budgets across the industry. Indeed, the company warned in March of "another year of challenging market conditions" across the upstream oil and gas and mining segments.

And the prospect of prolonged troubles beyond 2016 makes Amec a risk too far at present, even in spite of a low forward P/E rating of 8.7 times.

Sales shrinking

The jitters surrounding the retail sector, and consequently major high street players like Marks and Spencer(LSE: MKS), have gone up several notches in recent days.

Following a string of poor consumer confidence gauges following the EU referendum, researcher Nielsen turned up the dial on Monday by advising that 52% of respondents to a recent poll plan to save money by spending less on clothing. This is likely to hit demand for Marks and Spencer clothing, even though CEO Steve Rowe wants to make its everyday prices more appealing.

And today the British Retail Consortium announced that like-for-like UK retail sales slipped 0.5% in June, prompted by insipid clothing sales.

This bodes badly for Marks and Spencer as it struggles to get its Womenswear lines firing again -- sales of its clothing and homeware products tanked 8.9% during April-June. And constrained shopper spending power could also put paid to the electric revenues growth enjoyed at its Food division.

I've long been positive over Marks and Spencer's long-term outlook. But the Brexit vote has very much changed the game for the business, and I believe the retailer is now a risky pick despite a conventionally-cheap P/E rating of 10.7 times for fiscal 2017.

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Royston Wild has no position in any shares mentioned. The Motley Fool UK has no position in any of the shares mentioned. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.