Sanofi-Aventis' experimental drug aflibercept failed to meet its goal in a mid-stage ovarian cancer study but the French drug maker said on Wednesday it had shown some promising signs of effectiveness.
Sanofi is working on the drug, which belongs to the same class as Roche Holding and Genentech's Avastin, with its original developer Regeneron Pharmaceuticals .
Sanofi had previously said it planned to file aflibercept for regulatory approval later this year.
Analysts said they now expected a delay.
A Phase II study found single-agent aflibercept did not achieve its primary endpoint of demonstrating that patients achieved a response rate significantly greater than 5 percent, as assessed by an independent review committee, the companies said.
The response was 4.6 percent on the higher of two doses used, according to the committee.
However, as assessed by the study's investigators, the response rate was 7.3 percent.
Ben Yeoh, an industry analyst with Dresdner Kleinwort, said the failure to hit the primary endpoint was not a great surprise, since the findings were in line with interim data presented last year, and the news was only a slight negative. "Ovarian cancer is a very tough cancer, and it didn't miss by much," he said.
Sanofi and Regeneron said they were continuing to evaluate the data from the trial to determine the next steps for aflibercept in advanced ovarian cancer.
"We are encouraged by the results reported with the use of single-agent aflibercept in this advanced ovarian cancer patient population for whom few therapeutic options are available," Marc Cluzel, Sanofi's head of research, said in a statement.
Aflibercept is also being assessed in colorectal, pancreatic, prostate and lung cancer.
Shares in the company - the world's third-largest drug maker by sales - were 0.7 percent lower at 47.37 euros, with the DJ Stoxx European drugs index down 0.4 percent.
There were also some promising results from studies of aflibercept in symptomatic malignant ascites, which showed eight out of 10 patients achieved a repeat paracentesis response rate, the primary endpoint of the trials, the companies added.
Aflibercept, like Avastin, works by blocking the blood supply to tumors.
Analysts expect Avastin, which is approved for treatment of colorectal cancer and non-small cell lung cancer, to be one of the world's biggest selling drugs in the years ahead, but it faces competition from a clutch of products that work in a similar way.