Shares of Ardelyx, Inc. ARDX plummeted 73.9% following negative regulatory update related to its new drug application (“NDA”) seeking approval for lead pipeline candidate, tenapanor, as a treatment for hyperphosphatemia, an elevated level of serum phosphate in the blood, in patients with chronic kidney disease on dialysis.The company announced that the FDA identified deficiencies in the NDA, which prevent discussion related to labeling and post-marketing requirements/commitments currently. Although the FDA did not provide specific details regarding the deficiencies, it noted that the size of the treatment effect and its clinical relevance was a key issue. Moreover, the FDA denied a request for a meeting made by the company to discuss the deficiencies.The FDA also stated that the notification about deficiencies does not reflect its final decision related to the NDA.We note that Ardelyx submitted the NDA supported by data from three successful pivotal studies. The company also had a discussion related to labeling with the FDA in April. The unexpected deficiency notification from the FDA significantly impacted investors’ sentiments. However, the FDA had extended the review period for tenapanor NDA in April by three months.Shares of Ardelyx have declined 68.9% so far this year compared with the industry’s decrease of 11.9%.Image Source: Zacks Investment ResearchThe company’s tenapanor is already approved as Ibsrela for treating irritable bowel syndrome with constipation (IBS-C) in adults.However, we note that Ironwood Pharmaceuticals IRWD/AbbVie’s ABBV Linzess holds a strong position in the IBS-C segment. Bausch Health BHC has an IBS-C drug, Trulance, in its marketed portfolio. These drugs pose competition to Ibsrela.Ardelyx is also developing another pipeline candidate, RDX013, as a treatment for hyperkalemia — a condition of elevated level of potassium in the blood. The company has an ongoing discovery program for a bicarbonate exchange inhibitor for the treatment of metabolic acidosis.Ardelyx, Inc. Price Ardelyx, Inc. price | Ardelyx, Inc. QuoteZacks RankArdelyx currently carries a Zacks Rank #3 (Hold). You can see the complete list of today’s Zacks #1 Rank (Strong Buy) stocks here. Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $775 billion by 2024 as scientists develop treatments for thousands of diseases. They’re also finding ways to edit the human genome to literally erase our vulnerability to these diseases. Zacks has just released Century of Biology: 7 Biotech Stocks to Buy Right Now to help investors profit from 7 stocks poised for outperformance. Our recent biotech recommendations have produced gains of +50%, +83% and +164% in as little as 2 months. The stocks in this report could perform even better.See these 7 breakthrough stocks now>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Ironwood Pharmaceuticals, Inc. (IRWD): Free Stock Analysis Report AbbVie Inc. (ABBV): Free Stock Analysis Report Ardelyx, Inc. (ARDX): Free Stock Analysis Report Bausch Health Cos Inc. (BHC): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research