The United States District Court of Delaware has ruled that a generic drug proposed by Dr Reddy’s, an Indian pharmaceuticals group, did not infringe US patents on Suboxone film. Dr Reddy’s had bought Suboxone Film’s abbreviated new drug application (ANDA) from Teva Pharmaceuticals for $70 million in June 2016 with seven generic filers. The key patent expires in April 2024. However, Indivior said that it would appeal against the US court ruling.

Indivior can be added to that roll-call, the drug company having just seen its shares fall by almost 40% on a US court ruling. The decline has wiped more than £1bn from its stock market valuation

“The United States District Court, for the District of Delaware, issued its judgment in favour of Dr Reddy’s Laboratories, ruling that the proposed generic version of Suboxone (buprenorphine and naloxone) sublingual film does not infringe US Patent Nos. 8,017,150; 8,603,514 and 8,900,497 as asserted by Indivior,” Dr Reddy’s said in a statement.

“We are pleased with the verdict passed by the US District Court of Delaware in Dr Reddy’s favour, on the patent litigation of the drug Suboxone. The judgement reiterates our commitment to providing affordable and innovative medicines that address the unmet and under-met needs of patients around the world,” Dr Reddy’s spokesperson stated.

Suboxone (buprenorphine and naloxone) sublingual film is indicated for the maintenance treatment of opioid dependence. Reckitt Benckiser developed Suboxone sublingual film using MonoSol Rx’s PharmFilm technology. In December 2014, Reckitt Benckiser de-merged its pharmaceuticals business as Indivior.

Meanwhile, Indivior said that it would not be able to rely on patents to prevent Dr Reddy’s from making and marketing a generic alternative to Suboxone Film in the US, unless the court’s ruling was reversed on appeal. But investors were spooked by the threat to US sales of Suboxone Film, which account for 80 per cent of Indivior’s £817m global revenues, and shares were down 35.8 per cent, or 149p, to 267.6p. It went on: “A material loss in market share in the US would have a significant impact on the company’s revenues, profitability and cash flows.”