Organic arsenic drug darinaparsin is believed to be less toxic than inorganic compounds.

Solasia Pharma is paying Ziopharm Oncology $5 million up front as part of a license and collaboration agreement centered on developing and commercializing the latter’s Phase II-stage anticancer drug Zinapar™ (darinaparsin, or ZIO-101) and related organic arsenic molecules, in specific Pan-Asian/Pacific Regions.

The $5 million payment is to be used by Boston-based Ziopharm exclusively for further clinical development of darinaparsin outside of the pan-Asian/Pacific territory. The firm could also receive up to another $32.5 million from Solasia in development-based milestones, plus $53.5 million in sales milestones and double-digit sales royalties.

Solasia specializes in developing Western oncology products for Asian markets. Under terms of the darinaparsin deal the firm has exclusive rights to develop both intravenous and oral formulations of the drug and related organic arsenic molecules, for all human indications, in Japan, China, Hong Kong, Macau, Republic of Korea, Taiwan, Singapore, Australia, New Zealand, Malaysia, Indoneisia, Philippines and Thailand.  Solasia will be responsible for all development and commercialization activities in its designated countries. The two firms say they may look to carry out future joint development activities under a cost-sharing arrangement.

“Darinaparsin is well tolerated and is expected to be less toxic than arsenics commonly used in Japan, China, and other territories in Asia, and has demonstrated promising efficacy in hematologic cancers, including peripheral T-cell lymphoma, a disease nearly twice as prevalent in Asia compared to the West, but for which there are very few treatment options,” comments Steven E. Engen, Solasia president and CEO.

Darinaparsin is a mitochondrial-targeting agent in development for the treatment of a range of hematologic and solid cancers. Phase II studies in patients with primary liver cancer and advanced myeloma are nearing completion, and a Phase II trial is ongoing in lymphoma patients. A Phase I trial evaluating an oral formulation of the drug in solid tumors is also in progress. Ziopharm says intravenous darinaparsin has demonstrated clinical activity in lymphoma patients, and in particular those with peripheral T-cell lymphoma (PTCL). The firm projects starting a registrational trial evaluating the drug in PTCL patients (probably in the refractory setting) during late 2011.

Ziopharm is also evaluating the tolerability of a combination of darinaparsin with CHOP (cyclophosphamide, doxorubicin, vincristine and prednisone) standard of care therapy for PTCL, for possible future trials evaluating combination therapy in a front-line setting. Darinaparsin has been granted orphan drug designation in the U.S. and EU, and Solaris expects to file for orphan drug status in Japan.

Ziopharm has two additional anticancer candidates undergoing clinical development. Zymafos™ (palifosfamide, ZIO-201) is a functional active metabolite of ifosfamide, a standard of care for treating sarcoma, lymphoma, ovarian, testicular and other cancers. 

Palifosfamide is designed to deliver only the cancer fighting component of ifosfamide, which the firm suggests should help negate the problems of drug resistance that occur with ifosfamide and cyclophosphamide therapy for certain cancers. Palifosfamide in addition does not lead to the production of toxic metabolites of ifosfamide that can cause encephalopathy and severe bladder inflammation, Ziopharm adds. The drug is currently undergoing a Phase II study combined with doxorubicin as a treatment for unresectable or metastatic soft-tissue sarcoma. A single agent Phase II clinical trial in sarcoma has already been completed, while a Phase I study evaluating parlifosfamilde in combination with doxorubicin against soft-tissue sarcoma is in nearing completion. Plans for an oral palifosfamide study are in addition being planned.

The third clinical candidate in Ziopharm’s pipeline is Zybulin™ (indibulin, ZIO-301), an oral tubulin binding agent designed to target both mitosis and cancer cell migration. Indibulin is expected to have several potential benefits, including oral dosing, application in multidrug resistant tumors, no neuropathy and minimal overall toxicity, Ziopharm claims. The drug has already shown evidence of activity in a Phase I study as a single agent against a range of solid tumors. Indibulin is also currently in the Phase I stage of Phase I/II trials as combination therapy with either Tarceva® or Xeloda®. In December 2010 Ziopharm reported dosing the first patient in a Phase I, single-arm, dose-escalation study evaluating intravenous palifosfamide in combination with etoposide (VP-16) and cisplatin/carboplatin (platinum) in the treatment of small-cell lung cancer and other cancers.

Tokyo-based Solasis is dedicated to developing new anticancer drugs throughout the Asian region. The firm has Asian rights to ProStrakan’s Sancuso (extended-release granisetron transdermal patch), and is carry out clinical development of the drug in China. An NDA for Sancuso is expected to be filed with the Chinese regulatory authorities during 2011.

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