Did you catch all the big biotech stories last month? If you didn't catch all the big moves, don't worry. We've got you covered.

Here's what you need to know about three of the biggest biotech stock run-ups that happened in September.

Company (Symbol) Price Change During September 2021  Market Cap
Bellus Health (BLU) 66% $481 million
Leap Therapeutics (LPTX -1.56%) 133% $350 million
Kadmon Holdings (KDMN) 59% $1.5 billion

Data source: Yahoo! Finance.

Scientist examining sample tubes.

Image source: Getty Images.

1. Leap Therapeutics

Leap Therapeutics stock shot higher in response to positive data for its cancer drug candidate, DKN-01. This is a potential first-in-class antibody that targets Dickkopf-1. Too much Dickkopf-1 activity is associated with aggressive tumor growth, and it looks like regulating it with DKN-01 can make a big difference for stomach cancer patients.

Leap Therapeutics doesn't have any approved drugs to sell yet, and DKN-01 is the only candidate the company has in clinical-stage testing. It could be just a matter of time before Leap's lead asset becomes part of a new regimen that includes tislelizumab.

Tislelizumab is an already successful cancer immunotherapy from Beigene (BGNE 2.05%). It's a PD-1 inhibitor that prevents tumor cells from shutting down the immune system when it attacks. It is already approved in China, and it's under review in the U.S. at the moment.

We can expect Beigene to put all necessary resources behind DNK-01 because it appears to boost tislelizumab's efficacy. Treatment with the combination shrank tumors for 68% of the stomach cancer patients who received it.

Scientists at work in a lab.

Image source: Getty Images.

2. Bellus Health

Shares of this clinical-stage biotech soared last month after the company announced positive clinical trial data for its lead candidate. BLU-5937 is a potential first-in-class treatment for chronic cough and other conditions associated with hypersensitive nerve endings. 

Bellus Health's stock price jumped 66% last month because refractory chronic cough patients randomized to receive BLU-5937 instead of a placebo exhibited clinically meaningful reductions in coughing frequency. There was also an encouraging lack of serious adverse events.

Refractory chronic cough is a condition that affects an estimated 9 million patients in the United States alone. There aren't any available treatments for this large underserved population, so further success with BLU-5937 could inflate Bellus Health's stock price several times over.

The stock could have soared much higher, but the company didn't share any details regarding the data. That's a problem because Merck (MRK -0.30%) is developing a similar chronic cough candidate called gefapixant, and the pharmaceutical giant is a few steps ahead of Bellus Health. Compared to placebo, treatment with gefapixant reduced cough frequency by 22% at the lowest dose tested and 37% for the highest dose. If Bellus can report better numbers, its stock will explode higher, but that's far from guaranteed. 

Happy investor checking stocks on a tablet.

Image source: Getty Images.

3. Kadmon Holdings

Kadmon stock rocketed higher overnight after Sanofi (SNY -2.35%) agreed to acquire the biotech on Sept. 8. The buyout offer announcement came just weeks after the Food and Drug Administration approved Kadmon's lead asset, Rezurock, to treat chronic graft-versus-host disease (GVHD), which can cause adverse reactions in stem-cell and bone-marrow transplant patients.

In the U.S. alone, GVHD affects an estimated 14,000 patients, many of whom are in dire need of new treatment options. Sanofi was willing to pay a premium for Kadmon because Rezurock is the first and only approved treatment that acts on rho-associated coiled-coil kinase 2 or ROCK2.

Assuming the deal goes through without a hitch, Sanofi will give Kadmon shareholders $9.50 per share. That works out to a 79% premium compared to the biotech stock's closing price preceding the announcement. The addition of Rezurock could go a long way to bolster Sanofi's growing transplant business.