By Justin George Varghese
(Reuters) - Shares in Britain's Indivior were hammered on Friday after it lost a second legal case in recent months in its battle to protect the patent of its opioid addiction treatment that generates 80 percent of its revenues.
The stock fell 24 percent to a six-month low before clawing back most of that to trade 4.5 percent down at 390 pence at 1100 GMT, with analysts judging the risk of generic versions of the drug being launched soon as stil low.
A U.S. District Court ruled that American generic drugs maker Alvogen had not infringed three Indivior patents, the British company said, weakening its defense against rival versions of its big seller, Suboxone Film.
Indivior said it believed it has grounds to appeal.
The case comes six months after the Delaware District Court ruled Indivior could not rely on patents to stop Indian drugmaker Dr. Reddy's launching a generic version of Suboxone Film. Shares plunged 40 percent and have steadily been recovering since.
Generic rivals in tablet form are already on the market in the United States which is grappling with an opioid addiction epidemic that killed 33,000 people 2015.
But Suboxone Film leads the market for a version which is placed under the tongue to suppress cravings. Its U.S. market share was 56 percent at the end of 2017, down from 61 percent the previous year.
Indivior is also in patent disputes with Allergan Plc's Actavis Laboratories, Endo International's Par Pharmaceutical, Teva Pharmaceutical Industries and Mylan NV. Indivior settled a case with Mylan in September.
Analysts at Jefferies said the impact of the latest ruling was "less significant" than the September one and most companies would remain wary of launching a generic against Indivior and Dr. Reddy's was likely to be first.
"Any launch this year would be 'at risk' which we still see as unlikely; we would view any major share price correction as a buying opportunity," Jefferies analysts said in a client note.
Morgan Stanley analysts, took a similar view and forecast a generic entry by 2020.
Indivior launched a once-a-month injectable drug to suppress opioid craving in the United States this month. It hopes Sublocade will become a blockbuster medicine although expects initial sales to be slow.
Sublocade, which could be launched in Canada, Australia and Europe from late 2019, is designed to eliminate the risk that treatment drugs could be missed or misused.
(Reporting by Justin George Varghese in BENGALURU and Paul Sandle in LONDON; Editing by Robin Pomeroy)