Under the agreement with Novartis, Opexa received an upfront cash payment of $3 million and was entitled to an additional $1 million as a technology transfer fee to be paid over the course of a six month period. The $500,000 milestone is part of that $1 million technology transfer fee, Opexa said. Opexa shares, which have been all over the map this month, were lately up 62 cents, or 17.9%, to $4.08. As of 1:10 p.m. EDT, more than 7 million changed hands, which is nearly twice the stock's 50-day average daily volume, according to the Nasdaq's Web site. Opexa has a 9.46 million-share float, according to Yahoo! Finance. As my colleague Adam Feuerstein pointed out earlier this month, Opexa has seen volume surge and price volatility on assorted news items. The stock soared 270% on Sept. 9 to close at $5.66 after the company said "additional favorable data" from a previously completed phase II study of Tovaxin, a personalized immunotherapy, or "vaccine" for patients with relapsing-remitting multiple sclerosis, Feuerstein wrote. During that Sept. 9 session, the stock touched an intraday high of $6.93, a staggering gain of 353%. -- Written by Robert Holmes in New York.