New York (Press Release) - Stemline Thera­peutics, Inc. (Nasdaq:STML) an­nounced to­day that data demonstrating SL-401 ef­fi­cacy in mul­ti­ple myeloma (MM) pre­clin­i­cal models will be pre­sented at the American Society of Clinical Oncology (ASCO) Annual Meeting being held May 30-June 3, 2014 in Chicago, IL.

In col­lab­o­ration with Stemline, ex­per­i­ments con­ducted at the Dana-Farber Cancer In­sti­tute, Boston, MA, by Drs. Dharminder Chauhan and Kenneth Anderson and their MM re­search team dem­onstrated that Stemline's clin­i­cal can­di­date SL-401 sig­nif­i­cantly de­creased the viability of malignant cells by targeting neighboring plas­ma­cytoid dendritic cells (pDCs) in the tumor microenvironment of the bone mar­row. The re­searchers have pre­vi­ously shown that pDCs, which express the IL-3R, the target of Stemline's SL-401, promote MM growth, poten­tially via IL-3/IL-3R signaling. SL-401's novel ac­­tiv­ity against MM oc­curs at extremely low (picomolar) con­cen­tra­tions that are readily achievable in patients. Based on these results and prior data, SL-401 appears to have both direct (anti-MM) and indirect (anti-pDC) ac­­tiv­ity in this dis­ease.

The Dana-Farber re­searchers also dem­onstrated that SL-401 was active against MM cells obtained from patients resistant to standard agents used to treat MM in­­clud­ing bor­tez­o­mib (Velcade®), dexa­meth­a­sone, and lena­lido­mide (Revlimid®). Addi­tionally, SL-401 dem­onstrated syn­­er­gis­tic ac­­tiv­ity against MM cells when com­bined with bor­tez­o­mib, mel­phalan, lena­lido­mide, or poma­lido­mide (Pomalyst®). Finally, SL-401 was also found to in­hib­it the for­ma­tion of osteoclasts, which are the bone mar­row cells responsible for bone loss, fractures, and sig­nif­i­cant morbidity in MM patients. SL-401 also stabilized the for­ma­tion of bone-strengthening bone mar­row cells called osteoblasts.

Eric K. Rowinsky, M.D., Chief Medical Officer and Head of Research and De­vel­op­ment at Stemline Thera­peutics, noted, "Although many agents for mul­ti­ple myeloma have emerged over the last decade, these ther­a­pies ultimately fail. In such situations, new agents with unique mech­a­nisms of action, like SL-401, have provided addi­tional im­prove­ment in patient out­comes." He added, "We look for­ward to build­ing on these extraordinary results with SL-401 in MM which will serve as a foundation for its clin­i­cal devel­op­ment in this malig­nan­cy."

About SL-401

SL-401 is a novel targeted ther­apy directed to the interleukin-3 re­cep­tor (IL-3R), a target present on tumor bulk and cancer stem cells (CSCs) of mul­ti­ple hema­to­logic cancer indi­ca­tions. SL-401 has dem­onstrated clin­i­cal ac­­tiv­ity in sev­er­al indi­ca­tions, in­­clud­ing blastic plas­ma­cytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML), and myelo­dys­plastic syn­drome (MDS), as well as pre­clin­i­cal ac­­tiv­ity in mul­ti­ple myeloma (MM), chronic myeloid leukemia (CML), rare IL-3R+ cancers such as chronic eosinophilic leukemia, and cer­tain lymphoid leukemias and lym­phomas.

Details on the pre­sen­ta­tion are as follows:

Effect of a novel agent SL-401, targeting Interleukin-3 Receptor (IL-3R) on plas­ma­cytoid dendritic cell (pDC)-induced myeloma cell growth and osteolytic bone dis­ease
Lead Author: Dharminder Chauhan, Ph.D., Dana-Farber Cancer In­sti­tute
Authors: Dharminder Chauhan, Arghya Ray, Deepika Das Sharma, Vincent Macri, Christopher Brooks, Paul Richardson, Eric Rowinsky, and Kenneth C. Anderson
Abstract: #8599
Date and Time: Monday, June 2, 2014 - 1:15 to 5:00 PM CT
Location: S Hall A2
Poster Board: #286

A copy of the above referenced abstracts can be viewed online through the ASCO website at www.asco.org.

About Stemline Thera­peutics

Stemline Thera­peutics, Inc. is a clin­i­cal-stage bio­pharma­ceu­tical com­pany devel­op­ing novel on­col­ogy thera­peutics that target both cancer stem cells (CSCs) and tumor bulk in a variety of cancer types. Stemline is cur­rently devel­op­ing two clin­i­cal-stage prod­uct can­di­dates, SL-401 and SL-701. SL-401 is a targeted ther­apy directed to the interleukin-3 re­cep­tor (IL-3R). SL-401 has dem­onstrated single-agent ac­­tiv­ity, in­­clud­ing durable com­plete re­sponses (CRs), in a Phase 1/2 trial in sev­er­al indi­ca­tions in­­clud­ing blastic plas­ma­cytoid dendritic cell neoplasm (BPDCN) and re­lapsed or re­frac­tory acute myeloid leukemia (AML). SL-401 is being ad­vanced into pro­grams in BPDCN and other rare IL-3R+ malig­nan­cies, as well as addi­tional hema­to­logic cancers in­­clud­ing AML and myeloma. SL-701 is an en­hanced immuno­therapy that activates the immune sys­tem to attack tumors. An earlier version of this ther­apy dem­onstrated single-agent ac­­tiv­ity, in­­clud­ing durable CRs and partial re­sponses (PRs), in Phase 1/2 trials in ad­vanced adult and pedi­atric brain cancers. SL-701 is being ad­vanced into trials of adults with glio­blas­toma multiforme (GBM) at first recurrence, and chil­dren with non-brainstem and brainstem glioma. For more in­for­ma­tion about Stemline Thera­peutics, visit www.stemline.com.

Forward-Looking State­ments

Some of the state­ments in­cluded in this press release may be for­ward-looking state­ments that in­volve a num­ber of risks and un­cer­tain­ties. For those state­ments, we claim the pro­tec­tion of the safe harbor for for­ward-looking state­ments con­tained in the Private Se­cu­ri­ties Lit­i­ga­tion Reform Act of 1995. The factors that could cause our actual results to differ ma­teri­ally are identified from time to time in our reports filed with the Se­cu­ri­ties and Ex­change Com­mis­sion. Any for­ward-looking state­ments set forth in this press release speak only as of the date of this press release. We do not in­tend to up­date any of these for­ward-looking state­ments to reflect events or cir­cum­stances that oc­cur after the date hereof.