Shares of Aduro Biotech (ADRO) tanked by 16.65% today after the company announced that it had failed its phase 2b "Eclipse" trial in patients with pancreatic cancer. The phase 2b trial was testing the company's vaccine immunotherapy CRS-207, which is the company's most advanced drug in the pipeline. For the phase 2b trial the company was testing their drug either alone or in combination with another drug, GVAX Pancreas, against chemotherapy. 

The final results was that CRS-207 and GVAX Pancreas obtained a medial overall survival of 3.8 months, while CRS-207 alone performed better with an overall survival of 5.4 months, and chemotherapy alone obtained a median overall survival of 4.6 months.

Yes, CRS-207 alone was slightly higher than the 4.6 months of overall survival that chemotherapy obtained, but it is still not considered enough to be statistically significant. For the drug to have been statistically significant it would have needed a much larger difference from the chemotherapy treatment. These results came as an unhappy surprise, since results of the phase 2a study had been positive.

This is also bad news for another biotechnology company, Advaxis (ADXS), which uses the same type of technology. Both companies use reengineered listeria bacteria as antigens on cells, in order to generate a response from the immune system to come and kill the cancerous cells. Seems that investors should be cautious investing in either Aduro Biotech or Advaxis, after this trial showing that the technology may not work as well as many have hoped. 

There is still hope for a turnaround for Aduro. There is another pancreatic cancer trial, "Stellar," with results due later this year, that is testing Aduro's vaccine CR-207 in combination with both GVAX Pancreas and Bristol Myers' (BMY) Opdivo. Opdivo already has five FDA breakthrough-drug approved indications for types of cancer. The hope here is that the combination of all three treatments put together may yield better results than the ones presented today. Hopefully investors can recover losses, but for now it would be prudent to stay away from both Aduro and Advaxis.