Shares of Longeveron Inc. /zigman2/quotes/224642771/composite LGVN 0.00% blasted 120.9% higher on very active morning trading Thursday, after the biotechnology company said its Lomecel-B for the treatment of a congenital heart defect in infants (Hypoplastic Left Heart Syndrome) affecting about 1,000 babies a year was granted rare pediatric disease (RPD) designation by the Food and Drug Administration. Trading volume exploded to 112.0 million shares, compared with the full-day average of about 110,000 shares. The stock was both the biggest gainer and most active on major U.S. exchanges. The company said Lomecel-B is currently being evaluated in a Phase 2 trial. Despite the rally, the stock, which went public in February, was still trading well below the initial public offering price of $10 a share. The stock has now climbed 77.7% over the past three months, while the iShares Nasdaq Biotechnology ETF /zigman2/quotes/206189322/composite IBB +1.15% has slipped 8.8% and the S&P 500 /zigman2/quotes/210599714/realtime SPX +1.00% has gained 6.4%.