* Q3 sales of branded drugs jump 50 pct
* Q3 gross margin up more than 300 basis points
* Doesn't update forecast due to Pfizer talks
* Shares up 1.4 pct in premarket trading (Adds forecast, background; updates shares)
Nov 4 (Reuters) - Botox-maker Allergan Plc, which is in talks to be bought by Pfizer Inc, reported a better-than-expected quarterly profit on strong sales of high-margin branded drugs, its biggest business.
Shares of Allergan, created from the merger of Actavis and Allergan, rose 1.4 percent to $313.50 in premarket trading on Wednesday.
The Actavis-Allergan merger brought signature drugs such as Botox anti-wrinkle treatment and eye drops Restasis under one roof, freeing Allergan to enter into a deal to sell its generics business to Teva Pharmaceuticals Industries Ltd.
Allergan had said it expected revenue of more than $8 billion in the second half of the year. Since then, Allergan has entered into friendly buyout talks with Pfizer.
Dublin-based Allergan said on Wednesday it would not update its forecasts as that would need more disclosures, according to Irish takeover rules, with respect to its talks with Pfizer.
A merger between Allergan and Pfizer will be the biggest takeover deal this year and create the biggest healthcare company in the world.
Allergan said revenue from branded products jumped 50 percent to $2.39 billion in the third quarter ended Sept. 30, accounting for 58.5 percent of total revenue.
The business's gross margin improved to 87.9 percent from 84.1 percent.
The drugmaker's total revenue rose 90 percent to $4.09 billion, marginally beating analysts average estimate of $4.03 billion, according to Thomson Reuters I/B/E/S.
Allergan's net income was $5.23 billion, or $13.29 per share, including $15.64 per share from its generic drugs business.
The company posted a net loss of $1.04 billion, or $3.95 per share, a year earlier.
Excluding special items, Allergan earned $3.48 per share in the latest quarter, while analysts were expecting $3.18.
The company has now topped analysts' profit estimates for at least eight quarters in a row.
Allergan will host its annual R&D day with investors to discuss its drug development pipeline later on Wednesday. (Reporting by Vidya L Nathan in Bengaluru; Editing by Saumyadeb Chakrabarty and Savio D'Souza)