Plymouth Meeting biotech stock falls after FDA places cancer compound on "clinical hold"

Shares of Inovio Pharmaceuticals plunged more than 16 percent Monday after U.S. regulators placed the company's lead compound to treat cancer on clinical hold.

The Plymouth Meeting biotech firm said the Food and Drug Administration had "placed a clinical hold on its proposed Phase III clinical program for VGX-3100," an experimental immunotherapy designed to treat precancers and cancers caused by the human papillomavirus, or HPV.

Inovio said the FDA had requested more data relating to "the shelf life" of the company's Cellectra 5PSP immunotherapy delivery device. Inovio says that it expects a formal letter from the FDA with more information within 30 days and that it expects the Phase 3 trial will be delayed until the first half of 2017.

The trial has not yet started, enrolled, or dosed patients.

"Inovio is working diligently with the FDA to address its concerns and anticipates that the requested data will be available before the end of this year," the company said. The delay does not affect its other ongoing clinical studies, Inovio said.

The company announced in August that it had begun a clinical study of its experimental Zika vaccine in 160 healthy adult volunteers in Puerto Rico. It is developing the Zika vaccine with GeneOne Life Science in South Korea and academic collaborators, including the Wistar Institute in University City.

In July 2014, Inovio announced that a mid-stage Phase II trial in women met "efficacy endpoints" and represented a "significant step" in providing women and physicians with a non-surgical treatment for precancerous lesions" due to human papillomavirus.

HPV is the most common sexually transmitted disease. At any one time, about 11 percent of the world population is infected with the virus, the company said.

Inovio shares were down 16.39 percent, or $1.37, to $6.99 at the close of trading on the Nasdaq.