Rapt Therapeutics climbs after Leerink Partners upgrades to 'outperform'

** Shares of drug developer Rapt Therapeutics RAPT.O rise 4% to $25.42 premarket

** Brokerage Leerink Partners upgrades stock to "outperform" from "market perform," citing favorable outlook for lead drug RPT904, which is being developed to treat allergic diseases

** Brokerage also raises PT to $37 from $16, a 51.3% premium to the stock's last close

** RPT904 is a long-acting anti-IgE antibody targeting the same epitope as Roche ROG.S and Novartis' NOVN.S Xolair, but with better binding affinity and longer half-life, allowing less frequent dosing - brokerage

** Leerink estimates $2.1 billion in worldwide sales by 2035 for RPT904, with a 45% probability of success

** Leerink notes "Our confidence in the commercial opportunity ... is driven by the large number of patients with food allergy and the opportunity for RPT904 to improve on Xolair’s shortcomings"

** Stock up 93% YTD