The Food and Drug Administration has asked Dendreon Corp.  to stop using some promotional materials for Provenge, saying they are “false or misleading” because they omit or minimize the prostate-cancer drug’s risks and overstate its effectiveness.

Provenge, which was approved by the agency in late April, is seen as the first in a new class of cancer-fighting drugs that use a patient’s cells to stimulate the body’s immune system to fight cancer.
Dendreon this week reported initial Provenge sales of $2.8 million in the second quarter and said sales are growing at a brisk pace.

In a letter to the drugmaker dated Tuesday, Robert Sausville of the FDA’s Office of Compliance and Biologics Quality said the promotional materials include a misleading timeline and left out a warning that “final sterility test results are not available at the time of infusion.” The drug usually is delivered in a three-infusion course of treatment.

In addition, a chart titled “Kaplan-Meier Survival Rate Estimates” does not provide enough information to show the limits of the study described, the letter said.

A Dendreon spokeswoman said the company intends to comply with the FDA’s request.

The company’s shares were at $38.75, down 0.8 percent, in after-hours trading.