By Esha Dey and Garima Goel
(Reuters) - Oncolytics Biotech Inc's lead cancer drug did not show as much improvement in survival rates of patients with head-and-neck cancer as expected by investors, sending its shares down as much as 21 percent.
The company said the drug improved survival in patients without their cancer worsening compared with those receiving chemotherapy alone, but did not say whether these results were statistically significant.
Analysts, however, said the improvement was difficult to assess due to lack of data on analyses of the trial.
A late-stage trial showed that 88 patients getting Reolysin - in combination with chemotherapy drugs carboplatin and paclitaxel - had a median survival rate of 150 days without their cancer worsening, the company said on Thursday.
Patients receiving chemotherapy alone showed a median survival rate of 115 days.
However, a statistically significant increase was reported in the number of patients on Reolysin experiencing mild fever, chills, nausea and diarrhea.
The persistent low-grade fever led to dropouts, shrinking the pool of patients.
"There may have been some anticipation that there would be stronger statistically significant effect ... the late dropouts probably impacted that," Wedbush Securities analyst Gregory Wade said.
Oncolytics also did not provide sufficient data on overall survival, which was the main goal of the trial, as the data was distorted with patients dropping out of the trial receiving additional treatment.
The company is also studying Reolysin in pancreatic, ovarian, colorectal, lung, prostate, and breast cancers.
Reolysin was safe and well-tolerated in the clinical study, the Calgary-based company said.
Oncolytics shares were down 20.5 percent at C$2.09 on the Toronto Stock Exchange. The company's Nasdaq-listed shares were down 20 percent at $2.
(Editing by Don Sebastian, Sayantani Ghosh and Kirti Pandey)