Fallout from the Bristol Myers-Squibb hepatitis C clinical trial is spreading. Drugmaker Idenix announced Thursday that the FDA told the company to idle the test of its nucleotide polymerase inhibitor, IDX184, because a patient in a clinical trial for BMS’s nucleotide polymerase inhibitor suffered a cardiac event.

The FDA’s hold is a partial one, meaning the drug isn’t dead, but that Idenix cannot recruit patients for additional trials until the FDA and Idenix can hash out the details of just what those trials will consist of.

The hold comes just as IDX184 testing found its legs in February, after being put on a partial clinical hold that was imposed in September 2010. Idenix’s Douglas Mayers, EVP and chief medical officer, told MM&M via email that the 2010 directive added a year to the company’s clinical development timelines.

Despite Thursday’s setback, Mayers wrote that the company remains committed to the nucleotide polymerase inhibitor and noted that although BMS has a similar mechanism, “we believe that there are significant differences between IDX184 and BMS094, including an entirely different pro-drug approach.”

Barclays analyst Ying Huang wrote in an August 16 research note that BMS’ snafu puts Idenix in jeopardy even though there’s no evidence that it poses a heart risk. Mayer’s comments acknowledge the potential spillover effect.

“We have watched and continue to watch other programs in this space carefully, and we have seen how news of one company’s programs can affect perceptions of other companies’ programs,” he wrote.

Huang’s note reflects this sentiment: the analyst wrote that even though Gilead’s Phase III GS-7977 has not yet received such FDA scrutiny, “the regulatory risk is rising.”