Panmure Gordon views AstraZeneca's latest setback as a significant buying opportunity, sticking with its forecasts and 'buy' recommendation.The drugs giant was issued with a response from the US Food & Drug Administration (FDA) requesting additional analysis of data on Brilinta, causing a delay for the blood-thinning drug.However, the broker believes that if there was any hidden risk, it would have been seen at the advisory committee meeting in July."We believe the company has been negotiating strongly on the label and probably pushed it too far, so the Agency responded with a request of further analysis," says analyst Savvas Neophytou.While the company remains confident that a new clinical trial is not required - reducing the downgrade risk - the broker says that Astra remains its top pick and expects further upgrades to drive the share price.Target price is 3,600p and the 'buy' rating remains unchanged.