The news sent shares in the drugmaker plunging by a third to 255.6p at the opening bell in London.
Last month, Indian giant Dr Reddy’s launched a cut-price version of Suboxone – Indivior’s blockbuster treatment for opiate drug addiction.
The FTSE 250-listed group is adamant that the generic drug infringes on some of its patents and went straight to the court asking them to prevent Dr Reddy’s from selling it while the dispute is resolved.
A temporary restraining order was granted but Indivior said it has already seen the impact from the launch of the copycat into the US market in those few days between the launch and the TRO being granted.
“The company has observed recent accelerated market share loss for Suboxone of two-and-half percentage points, to 52 percent, in the most recent weekly data,” read this morning’s statement.
“While the eventual impact could be materially higher depending on Dr Reddy's final stocking levels, Indivior currently anticipates the FY 2018 net revenue impact from this level of share loss to be US$25mln.”
Given the impact already seen and the potential for greater losses, Indivior said its current full-year guidance – net revenue of between US$1.13-1.17bn and adjusted net income of US$280-320mln – is “no longer valid”.
Indivior relies heavily on Suboxone, which makes up about four-fifths of its total annual sales.
To try to reduce the dependence, the drug make has launched Sublocade – an injectable version of its best-selling drug. It had hoped this would make up for some of the shortfall in Suboxone but that hasn’t been the case so far.
Indivior still has hopes for Sublocade to be a blockbuster drug in its own right but now expects sales to be around US$50mln lower than previous forecasts due to “friction in the new distribution and reimbursement model”.
Chief executive Shaun Thaxter said: “Given the swift and material change in US market dynamics as well as the early-stage reimbursement and distribution model challenges we are experiencing with Sublocade, we are removing our FY 2018 net revenue and net income guidance.
“We are continuing to monitor US market developments to better gauge Dr Reddy's launch impact.
“We know that they are skilled in rapid distribution in quantity and, as such, there is a range of uncertainty around the amount of product they were able to ship before the temporary restraining order was granted by the court.”
Thaxter added that Indivior was looking to make US$25mln worth of cost saving to mitigate the dip in sales.