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Stemline Therapeutics Is First Biotech IPO of 2013

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By Peter Winter
BioWorld Insight Editor

Despite the positive reception that the Street afforded Intercept Pharmaceuticals Inc. and Kythera Biopharmaceuticals Inc., which each priced their initial public offerings (IPOs) at the top end of their ranges on the same day back in October, the bullish response to those two biotech offerings was not, it turned out to be, a harbinger for others to quickly follow suit.

After a gap of three months, New York-based Stemline Therapeutics Inc. became the first biotech IPO to launch in the new year. The company priced its IPO of 3.3 million shares of common stock at $10 per share, at the low end of its range of $10 to $12. It did, however increase the number of shares on offer by 1 million – a significant jump from the revised terms set for its offering. (See BioWorld Today, Jan. 11, 2013.)

Stemline granted the underwriters a 45-day option to purchase up to 497,647 additional shares of common stock to cover overallotments, if any.

Stemline, which will trade on Nasdaq under the symbol "STML," also became the second company to price an IPO that is focusing on therapies that target cancer stem cells, which typically comprise about 1 percent to 5 percent of a tumor but give rise to 95 percent or more of tumor cells known as the "tumor bulk."

Exactly one year ago, Verastem Inc., of Cambridge, Mass., priced a $55 million IPO, selling 5.5 million shares of its common stock at $10 per share. (See BioWorld Today, Jan. 30, 2012.)

Verastem is developing small-molecule inhibitors of signaling pathways that are critical to cancer stem cell survival and proliferation, including focal adhesion kinase (FAK), PI3K/mTOR and Wnt.

The company also recently in-licensed exclusive worldwide rights from Pfizer Inc. to VS-6063, an FAK inhibitor that has completed a Phase I study in advanced solid tumors. VS-6063 is expected to enter a Phase II mesothelioma study in mid-2013.

Among Stemline's lead drug candidates are SL-401, a biologic drug conjugate that targets the interleukin-3 receptor, and SL-701 , a synthetic peptide vaccine initially targeting pediatric and adult brain cancer, both of which, the company reported, have demonstrated single-agent clinical activity in Phase I/II studies in advanced cancer patients.

In December, Stemline released data from two studies of SL-401 in acute myeloid leukemia (AML) and other hematologic malignancies, including blastic plasmacytoid dendritic cell neoplasm (BPDCN), and preclinical activity against Hodgkin's lymphoma. Updated clinical trial results for SL-401 suggested the therapy was well tolerated at clinically active doses and showed single-agent antitumor activity in heavily pretreated patients with AML as well as in patients with high-risk myelodysplastic syndrome and relapsed/refractory BPDCN. A single cycle of SL-401 demonstrated single-agent activity in patients with relapsed or refractory AML, including two durable complete responses of eight months and greater than 25 months duration, respectively, and multiple additional cases of leukemia blast reductions. (See BioWorld Today, Dec. 10, 2012.)

SL-401 is being advanced into a pivotal Phase IIb trial in patients with BPDCN and a registration-directed Phase IIb study in patients with advanced AML.

Stemline's second clinical-stage therapeutic, SL-701, has demonstrated single-agent activity, including durable complete responses and partial responses in adult patients with refractory or recurrent glioblastoma and pediatric patients with malignant glioma, as well as an overall survival benefit in adult patients with refractory or recurrent glioblastoma compared with historical data.

Stemline got off to a flying start on its first day of trading closing at $11.80, up an impressive 18 percent, or $1.80.