Moleculin Biotech Inc. agreed to sell up to $20 million of its common shares to private equity firm Lincoln Park Capital LLC.

Chicago-based Lincoln Park Capital, which invests in both public and private companies, will buy the shares at Moleculin Biotech's request over a 36-month period.

Shares sold under the purchase agreement will be limited to 19.99% of the Houston-based cancer drug developer's outstanding common stock.