The House Energy & Commerce Committee, which is investigating the “potentially premature” return to market of ProHeart 6, a controversial drug used to prevent heartworm in dogs, notes that the med contains moxidectin. And the ingredient is also found in a drug being tested on humans in Ghana for preventing and treating river blindness. Wyeth hopes its drug is better than Mectizan, a widely used Merck med.

Why does the committee care? ProHeart 6 was yanked in 2004 after being linked to an unusually high rate of deaths and serious side effects following a review by an FDA vet. However, Wyeth then launched a secret investigation into the vet; raised conflict-of-interest charges against her at the FDA; and implicitly threatened FDA officials that further action would be pursued if the vet was allowed to remain in place. She eventually took a different position at the agency.

Meanwhile, a 2005 FDA advisory committee met to evaluate the safety and risks associated with ProHeart 6 and recommended more data, including targeted animal safety studies, was needed. However, the recent Wyeth application for ProHeart 6 indicates the panel “did not require target animal safety studies for this supplemental approval.” The committee last month asked the FDA to explain its recent decision to allow ProHeart 6 back on the market.

Now, the committee reads in TDR News that a 2004 phase II trial for moxidectin in Ghana was delayed due to the ProHeart 6 controversy, but an informal meeting was held the next year with independent experts from France, Nigeria and the Sudan, as well as Ghanan regulatory authorities and a national ethics review committee, to safey data summaries. The panel concluded that a phase II trial should begin as soon as possible, which it did in September 2006.

“Given that a 2005 FDA Veterinary Medicine Advisory Committee meeting composed of independent experts determined that ProHeart 6, containing moxidectin, is not safe for use in dogs,” the House committee wants to how officials in Ghana determined, at around the same time, that it was “safe to proceed” with the phase II trial in humans. And so John Dingell, the Michigan Democrat who chairs the commitee, and Bart Stupak, who heads the subcommittee on government oversight and investigations, wrote Wyeth demanding answers.

UPDATE: A Wyeth spokesman says the drugmaker will respond to the committee shortly, and adds that WHO is evaluating initial safety data from the phase II trial and so far, no differences were detected from the Merck drug.

Wyeth is conducting the trial in Ghana in collaboration with the Special Programme for Research and Training in Tropical Diseases, which is sponsored by the United Nations Children’s Fund, United Nations Development Programme, World Bank, and World Health Organization.