The memory of Merck & Co. Inc.’s $10 billion takeover last year of inhaled respiratory drug specialist Verona Pharma plc may not have been far from the minds of Wall Street speculators as Avalyn Pharma Inc. priced its IPO, selling about 16.6 million shares at the high end of the targeted range, or $18 each, to reap about $300 million. The stock (NASDAQ:AVLN) came out of the gate strong on the first day of trading and closed April 30 at $29.49, up $11.49, or 64%.