PTC Therapeutics (NASDAQ:PTCT - Get Free Report) announced that its Board of Directors has approved a stock buyback program on Tuesday, November 3rd, RTT News reports. The company plans to repurchase $500 million in shares. This buyback authorization permits the biopharmaceutical company to repurchase up to 9.8% of its shares through open market purchases. Stock buyback programs are generally a sign that the company's leadership believes its sha…