Summer is officially over, and the warm weather volume lull is has come to an end. It’s time for money movers to get back in front of their machines, and traders to get back at their desks. This time of year always brings with it a surge in volume. Combine that with a biotech catalyst, and there’s plenty of momentum to be taken advantage of.

Here are two of the biggest movers so far this week, and a look at what’s driving the action in each.

First up, Retrophin Inc (NASDAQ:RTRX). Retrophin was made infamous last year when its founder, Martin Shkreli, hit headlines for all the wrong reasons. The company had already sacked him by the time the real issues began, and he was long gone by the time he was indicted, but his shadow still hangs over the name, and any good news is a welcome break fro the negative sentiment. Well, shortly before markets opened on Wednesday, Retrophin announced the latest data from its kidney disorder drug, sparsentan. The drug is targeting a rare kidney disorder called focal segmental glomerulosclerosis, or FSGS, for which the major symptom is a progressive scarring of the kidney tissue and – eventually – kidney failure. There’s no current cure for the condition, and Retrophin is hoping to be first to market with its candidate.

The data showed significant reduction in proteinuria, one of the key baseline measurements for patients with this condition, post treatment, when compared to a generic SOC, and the drug was well tolerated and safe. Estimates put peak sales for a drug that is effective in treating this condition at more than $600 million, so an approval for a company like Retrophin, which is currently valued at a little over $800 million, is a big deal. Markets recognize this, of course, and the company is up nearly 40% mid-session US on Wednesday.

Next up, Agios Pharmaceuticals Inc (NASDAQ:AGIO).

Agios just announced that its partner, Celgene Corporation(NASDAQ:CELG), is set to disclose a new drug application submission at the Citi 11th Annual Biotech Conference in Boston – a move that would serve as a bold move from both companies (the application will be based on phase I/II data) and could trigger a wave of similar accelerated approval applications if succesfull. The drug in question is called enasidenib, and it’s targeting a rare form of leukemia called isocitrate dehydrogenase 1 (IDH1) mutant-positive AML. At the late stage (the target population) there’s essentially no options currently available for these patients. With the drug having proven safe, Celgene is going for approval based on potential benefit, and will then submit later stage data to the agency as and when it comes in.

Analysts suggest that this move will essentially bring Agios’ business plan two years ahead of schedule (assuming approval, of course) and that’s the driver behind the gains today. The company is up close to 25% mid session US, and just as with Retrophin, looks like it’s going to pick up more strength heading into session close.