Digging through old data to salvage a seemingly failed Alzheimer’s drug paid off big time for Biogen Inc., but at least one of its rivals has no plans to follow suit.

Eli Lilly & Co. Chief Executive Officer David Ricks said the pharmaceutical giant wouldn’t be revisiting a study that found its own promising drug failed to slow the progression of Alzheimer’s. To do so would be to call into question their research methods, Ricks said.

“It is a surprising set of events,” Ricks said in an interview on Wednesday. “It’s important that the scientific method is intact. You have to call your shot and if you hit it, you have confidence that medicine is working. It’s important that people, patients have confidence in your studies.”

Seven months after halting study of its experimental drug aducanumab, Biogen jolted the medical world on Tuesday by saying that it would attempt to get it approved. If the U.S. Food and Drug Administration signs off, the medicine would be the first that could arrest the memory-destroying disease to reach market.

Numerous drugmakers have tried and failed to develop similar medicines.

Lilly reported disappointing late-stage data for its experimental treatment solanezumab in 2016. The Indianapolis-based drugmaker has invested more than US$3 billion in Alzheimer’s research, but has so far failed to produce a candidate that could soon reach patients.

“Solezenamab showed a reduction but it was not statistically significant, so we moved on,” Ricks said, adding that the company has no plans to rehash that data. Lilly is pursuing a fourth study of the asset.

Biogen’s announcement surprised investors, doctors and researchers, and many are skeptical that a previously unsuccessful trial could bring a drug to market that would make a meaningful difference for millions of patients who suffer from the disease.

Alzheimer’s trials must assess many patients, Ricks said. “If you eliminate one population and include another,” he said, “you can always get very different answers.”

Still, “it’s good news when someone else gets a glimmer of hope,” Ricks said. “This is a tough space.”

Ricks said that if Biogen’s new finding that a higher-dose of its drug improved patient outcomes is legitimate, it “would be very encouraging for Lilly,” which is testing solezenamab at a four-times higher dose in elderly individuals who don’t have a Alzheimer’s diagnosis but may be at risk. The trial will read out in mid-2022.