** Shares of drug developer Arrowhead Pharmaceuticals ARWR.O fall 11.6% to $14.91

** Bernstein analyst William Pickering says ARWR's price action reflects "increasing investor concern on partner Sarepta's SRPT.O ability to pay Arrowhead $300 million in near-term milestones" due under their 2024 partnership

** Last year, Arrowhead signed a license and collaboration agreement with Sarepta for multiple clinical and preclinical programs

** Sarepta Therapeutics' shares down 4% at $13.49

** The concerns stem from recent deaths of patients treated with Sarepta gene therapies including Elevidys; company has also refused to comply with FDA's request on Friday to halt shipments of Elevidys

** B. Riley Securities analyst Madison El-Saadi says "SRPT-partnered neuromuscular candidates are high-value and are of investor interest"

** El-Saadi calls ARWR's partnered drug programs "a lifeline" for SRPT

** Pickering also notes that "Arrowhead stock has a history of very large swings on news perceived to impact its cash position and liquidity"

** Including session's moves, ARWR down 21% YTD and SRPT down 90%

(Reporting by Kamal Choudhury in Bengaluru)

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