What happened? Shares of Supernus Pharmaceuticals (NASDAQ: SUPN) are up by 16.7% as of 2:18 p.m. EST on Wednesday after rising by as much as 22.4% earlier today. Investors are bidding up shares of the biopharmaceutical company following its release of positive results from a phase 3 clinical trial for one of its leading pipeline candidates. So what A phase 3 trial investigating the efficacy of Supernus Pharmaceuticals' SPN-812 on adults with attention deficit hyperactivity disorder (ADHD) showed that the medicine was able to improve the symptoms of the condition when compared to the placebo, which was the study's primary endpoint. The drugmaker also reported that SPN-812 had a favorable safety profile throughout the study. Note that this medicine has already been reviewed by the U.S. Food and Drug Administration (FDA) for the treatment of ADHD in patients between the ages of 6 and 17. Image source: Getty Images. Back in November, the health regulatory agency issued a Complete Response Letter (CRL) to Supernus Pharmaceuticals indicating that it could not approve the drug yet due to concerns unrelated to SPN-812's safety and efficacy. The company will meet with the FDA in January to discuss the next steps for the potential approval of SPN-812 for patients aged 6 through 17, and if all goes well, Supernus Pharmaceuticals will submit another application for the drug, this time for adult ADHD patients, in the second half of 2021. Now what Supernus Pharmaceuticals is an intriguing play for those looking for under-the-radar biotech stocks to invest in. In addition to SPN-812, which could win regulatory approval and go on to tap into a "significant market opportunity" in the ADHD market, the company is also developing other medicines for central nervous system disorders, including epilepsy, depression, and Parkison's disease. Of course, there is always the possibility of clinical trial failure or regulatory setbacks, which is why interested investors should consider the risks first, and for those who decide to initiate a position, it is probably best to start small. 10 stocks we like better than Supernus PharmaceuticalsWhen investing geniuses David and Tom Gardner have a stock tip, it can pay to listen. After all, the newsletter they have run for over a decade, Motley Fool Stock Advisor, has tripled the market.* David and Tom just revealed what they believe are the ten best stocks for investors to buy right now... and Supernus Pharmaceuticals wasn't one of them! That's right -- they think these 10 stocks are even better buys. See the 10 stocks *Stock Advisor returns as of November 20, 2020 Prosper Junior Bakiny has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.Source