The push to develop new medicines isn't taking a break for the holiday season. In fact, the rest of December could be a busy couple of weeks.

All of these drugmakers are expecting big catalysts that could send their stock prices soaring or diving. Here's what to look for in the weeks ahead.

Company (Symbol) Market Cap Gain (Loss) Since Jan. 1, 2019 
Axsome Therapeutics (NASDAQ:AXSM) $1.71 billion 1,620%
Solid Biosciences (NASDAQ:SLDB) $196 million (-84%)
Intra-Cellular Therapies (NASDAQ:ITCI) $709 million 13%

Data source: Yahoo! Finance.

1. Axsome Therapeutics: A new antidepressant

Axsome Therapeutics has been the industry's top-performing stock this year, and it could climb much further soon. In October, the company finished enrolling around 300 patients with major depressive disorder (MDD) into a phase 3 trial with its lead candidate, AXS-05, and the results are expected before the end of the year.

In January, we learned that AXS-05 produced surprisingly strong proof-of-efficacy data in an 80-patient phase 2 trial. Over six weeks, the average depression rating score was significantly lower among patients treated with AXS-05 than those given an old antidepressant called bupropion. By week six, 47% of patients treated with AXS-05 achieved remission, compared with just 6% of the group given bupropion.

An estimated 7.1% of adults in the U.S. experience MDD each year, and available antidepressants aren't effective enough for a majority of them. If AXS-05 can repeat the success witnessed in phase 2 in the larger study, this stock will continue soaring.

Scientist using a microscope.

Image source: Getty Images.

2. Solid Biosciences: On hold

Solid Biosciences stock has tumbled this year in response to a clinical hold the FDA placed on its lead candidate. The company plans to report the data it has already collected by the end of the year, which could help the stock bounce back.

Solid's experimental gene therapy, SGT-001 for patients with Duchenne muscular dystrophy (DMD), transfers a portion of the dystrophin gene to muscle cells so they can produce their own dystrophin. The FDA slapped a hold on the SGT-001 program in response to a severe immune system reaction from one of six patients treated so far.

Before the end of the year, Solid Biosciences plans to present data from follow-up biopsies of actual muscle tissue. If SGT-001 helped DMD patients produce enough functional dystrophin to prevent chronic muscle damage, the FDA could be persuaded to overlook safety concerns and allow Solid to continue dosing new patients. That could go a long way to help Solid shares recover some of the year's previous losses.

Hand holding three cubes that spell FDA.

Image source: Getty Images.

3. Intra-Cellular Therapies: Schizophrenia

The FDA is expected to announce an approval decision on Dec. 27 regarding Intra-Cellular's lead candidate, lumateperone. It's been a few years since the company announced positive schizophrenia results from phase 3 studies used to support an application currently under review.

The agency postponed its review earlier this year to incorporate toxicology data from animals exposed to lumateperone. The FDA didn't feel an independent advisory committee meeting was necessary for lumateperone, which could be a positive sign.

Schizophrenia could be the first indication lumateperone earns approval to treat, but it probably won't be the last. The company could submit another application to expand its use to patients with bipolar depression based on successful phase 3 results the company presented earlier this year.

Bipolar depression and schizophrenia aren't nearly as common as MDD, but patients and their physicians need new treatment options. That means lumateperone sales could cross the $1 billion threshold in a few short years after its potential launch in 2020.

Man with fingers crossed and eyes closed.

Image source: Getty Images.

Safety nets?

All three of these biotech stocks could rocket higher if upcoming events play out in their favor, but these catalysts could cut both ways. None of these companies has a steady source of revenue yet, but the safety nets underneath them are very different. 

If Solid Biosciences can't get its gene therapy into the clinic again, there aren't any other clinical-stage programs in its pipeline to fall back on. If the FDA isn't willing to approve Intra-Cellular's schizophrenia candidate, the company has a potential treatment for heart failure in mid-stage testing already, but that's about it.

Axsome Therapeutics has a lot riding on its lead candidate, but not nearly as much as Solid Biosciences and Intra-Cellular. If AXS-05 happens to fizzle out, the company's pipeline sports a potential new migraine treatment in phase 3 testing and a potential new narcolepsy treatment that's expected to begin a phase 3 trial 2020.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.