SOUTH SAN FRANCISCO (AP) — Poniard Pharmaceuticals Inc. said Monday its cancer drug candidate picoplatin did not help lung cancer patients live longer, sending its shares plunging in early trading. Poniard was running a late-stage trial of picoplatin as a secondary treatment for non-small cell lung cancer, meaning the drug was given to patients who had previously been treated for the disease and had a relapse. But patients who received picoplatin did not live significantly longer than those who received the best supportive treatment, the company said. Results are based on data from 401 patients. Poniard said more of the patients on best supportive care had received chemotherapy in the past, which might have affected the trial results. The company said it will discuss the results with the Food and Drug Administration. In premarket trading, Poniard stock tumbled $5.86, or 77.3 percent, to $1.72. The shares closed at $7.58 Friday and have traded between $1.05 and $9.14 in the last year.