** Shares of drugmaker Phathom Pharmaceuticals PHAT.O rise 134% to near 7-month high of $11

** Co's request to the US FDA to update the "Orange Book" has been approved, granting its stomach infection medication, Voquezna, a 10-year exclusivity period

** Stock set for its best day on record, if gains hold

** The exclusivity period will prevent other firms from making similar versions of Voquezna

** Phathom filed a citizen petition to the FDA last year, seeking this exclusivity

** This exclusivity was initially granted to other versions of the drug, Voquezna Paks, which contain the same active ingredient as Voquezna

** Exclusivity protection will extend through May 3, 2032

** Including session's moves, stock up 31% YTD

(Reporting by Kamal Choudhury in Bengaluru)

((Kamal.Choudhury@thomsonreuters.com;))