By Mary Welch
NeXstar Pharmaceuticals Inc. entered a three-part collaboration with Glaxo Wellcome plc that includes a $10 million equity investment by Glaxo and a license for use of NeXstar's Selex drug discovery process with the pharmaceutical firm's functional genomics programs.
Under terms of the agreement, London-based Glaxo will employ the Selex combinatorial chemistry technology to enhance its functional genomics efforts by using aptamers to identify which genes or gene products are critical to disease progression and would be good targets for drug discovery.
An aptamer is a compound identified in the Selex process. Since each aptamer has a different shape and size, scientists can determine those that form a tight specific fit with a desired therapeutic target — thus increasing the odds that a drug candidate will be effective. To date, five different Selex-derived aptamers have shown benefit in animal disease models.
Aptamers have a direct role as drugs, but they also may be used in preclinical disease models to assess the potential therapeutic benefit of altering the activity of a specific gene product. Ultimately, aptamers may be able to confirm the role of the targeted molecule prior to starting a drug development program.
"Glaxo will be able to use Selex to identify targets in the development or progression of disease, and to see which genes cause a disease and which just play a role," said Anna Sussman, manager of investor relations for NeXstar, in Boulder, Colo.
In addition to the non-exclusive research license, Glaxo received certain rights to develop aptamers as therapeutics in return for milestone and royalty payments.
Anticancer Drug Also Part Of Pact
The second part of the agreement gives NeXstar an exclusive license to develop Glaxo's proprietary topoisomerase I inhibitor, lurtotecan, which showed encouraging antitumor activity in a completed Phase II program.
NeXstar has produced a liposomal formulation of lurtotecan, NX211. A liposome is a microscopic fat bubble that can be used to deliver drugs to specific areas of the body. "It encapsulates the drug and it prevents the drug from leaking into other parts of the body. It means that you can give a higher dosage of the drug and there are also fewer side effects," Sussman explained.
NX211 underwent preclinical studies that showed it produced a three-fold increase in therapeutic index as compared to the conventional drug. The studies concluded NX211 might be more effective and less toxic than lurtotecan and other topoisomerase inhibitors alone. NeXstar plans to start Phase I studies within the next 12 months to test NX211 against ovarian cancer.
As part of this deal, NeXstar Pharmaceuticals will make milestone and royalty payments to Glaxo. In addition, Glaxo has the option to participate in further development of the product in exchange for a licensing fee and sharing development costs. If Glaxo exercises that option, the companies would copromote the drug.
NeXstar already has two liposomal products on the market: AmBisome, a liposomal form of amphotericin B for systemic fungal infections, and DaunoXome, a liposomal form of the anticancer agent daunorubicin for HIV-associated Kaposi's sarcoma.
The third part of the Glaxo collaboration involved its purchase of 962,117 shares of NeXstar at $10.39 per share for a total of $10 million. NeXstar has 27 million shares outstanding.
NeXstar's stock (NASDAQ:NXTR) closed Wednesday at $10.50, up $0.031. *