Shares of Indivior (INDV.L) traded sharply lower early Thursday as the British drugmaker cut the sales outlook for Sublocade, a treatment for opioid use disorder, saying it “substantially underestimated” the lag time associated with the approval of medical benefits coverage of individual patients.

Net sales from Sublocade in the fiscal third quarter are likely to be $3 to $4 million, compared with an earlier forecast of $25 to $50 million for the full year, the firm said in a trading update. Indivior, which now conservatively assumes a linear trend in the prescription journey, said revenue from the treatment is expected to be $8 and $10 million in the full year 2018.

Additionally, Indivior also warned that it now expected the group net turnover of $990 million to $1.02 billion and adjusted net income of $230-$255 million for fiscal 2018. In February, it had forecast 2018 net revenue of between $1.13 billion and $1.17 billion and adjusted net profit of $290 million to $320 million at constant currency and excluding exceptional items.

“While we have yet to see the expected inflection in net revenues, each of the key launch metrics that we have previously highlighted continues to improve,” Chief Executive Officer Shaun Thaxter said in the statement. “Looking further out, we remain confident in achieving peak Sublocade net revenue of $1 billion-plus.”

Shares of Indivior slumped by more than 18%, the worst performing stock in the FTSE All-Share Index, at the time of writing in London.

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