CAMBRIDGE, Mass. (AP) — Biotech drugmaker Merrimack Pharmaceuticals Inc. said Friday that its second quarter loss narrowed as revenues doubled during its first period as a publicly traded company.

The company reported a net loss of $20.1 million, or 22 cents per share, compared with $29 million, or $2.76 per share in the second quarter of 2011. Analysts polled FactSet expected 27 cents per share.

Revenue for the period increased to $12.1 million from $6.6 million in the prior year period, due to milestone payments from its work developing experimental cancer drug MM-121 for Sanofi.

The company's research and development costs declined to $28.8 million, compared with $31.2 million, as the company wrapped up studies of cancer drug MM-398.

In April 2012, Merrimack closed the initial public offering of its common stock, selling 15 million shares of common stock at $7 per share.

Its shares rose 4 cents to $7.41 in afternoon trading. They have traded in a range of $5.66 to $9.20 since the IPO.