Idenix Pharmaceuticals Inc's experimental hepatitis C drug was placed on a partial hold by the U.S. health regulator, barely two weeks after Bristol-Myers Squibb Co's hepatitis C treatment encountered a heart-related safety issue.
Idenix shares dropped 35 percent in morning trade.
The U.S. Food and Drug Administration wanted to further review its drug, called IDX184, citing the serious heart-related adverse event seen in a competitor's drug, Idenix said in a statement.
Idenix did not name the competitor but Idenix's IDX184 and Bristol's drug BMS-986094 were both being tested in mid-stage trials and both belong to a promising new class of hepatitis C medicines known as nucleotide polymerase inhibitors.
The FDA has requested additional data on patients treated with IDX184 and Idenix said in a statement it plans to have an ongoing discussion with the FDA following the data submission.
Under the partial clinical hold, Idenix cannot enroll patients into additional trials until an agreement is reached with the FDA on the next trial design.
On a conference call with analysts, Idenix said it would need to provide results from echocardiogram (ECG) tests on 67 patients who were in the trial.
Nucleotide polymerase inhibitors work by targeting polymerase, an enzyme essential for the replication of the hepatitis C virus, and are expected to be a game changer.
Most hepatitis C drugs used today are combination therapies that include interferon. This causes unpleasant flu-like symptoms and other side effects, leading many patients to discontinue or delay treatment.
The nucleotides, or nucs as they are commonly called, do not use interferon.
The hepatitis C virus is the most common cause of viral hepatitis, an inflammation of the liver. It affects about 170 million people worldwide and the market for its treatments is expected to reach around $15 billion by 2019.
Idenix shares have nearly doubled over the last 12 months, while other nuc makers Inhibitex and Pharmasset had seen their shares rise manifold over the last year before getting bought out by Bristol and Gilead Sciences Inc, respectively.
Idenix shares were down 28 percent at $5.97 in morning trading on the Nasdaq. They fell to $5.40 earlier in the day.
Shares of Achillion Pharmaceuticals Inc, another hepatitis C drug developer, rose 4 percent in morning trade.
(Reporting by Esha Dey in Bangalore, Additional reporting by Pallavi Ail and Vidya P L Nathan; Editing by Rodney Joyce and Don Sebastian)