By Randall Osborne

West Coast Editor

Having cloned and expressed protein from an animal model, Zonagen Inc. said it¿s ready to begin a study that could lead to a human immunocontraceptive vaccine, and American Home Products Corp. has signed an option agreement for a potential $22.5 million licensing deal.

The agreement includes a collaborative, 18-month study in primates, said Louis Ploth, vice president of finance for The Woodlands, Texas-based Zonagen.

¿Any time during that period, and up to 60 days after the final report, they can exercise their option,¿ Ploth said, which would give AHP¿s Wyeth-Ayerst Laboratories division worldwide rights in exchange for an up-front fee and milestones together valued at up to $22.5 million.

Data published in September in The Journal of Reproduction and Fertility showed Zonagen¿s recombinant zona pellucida vaccine induced infertility in a primate model without permanent disruption of the menstrual cycle.

¿We¿re expanding some of the parameters of things to look at [with Wyeth-Ayerst],¿ Ploth said, but declined to be more specific. ¿There are not many contraceptive players,¿ he added. ¿They¿re huge, but very few.¿

The fact that Zonagen¿s approach, using the immune system rather than hormones, drew attention from the likes of AHP is encouraging ¿ especially given the preclinical nature of the research, said Ploth, who put the deal together.

¿I did the Vasomax deal, too [with Madison, N.J.-based Schering-Plough Corp.], but we had Phase III data when we closed it,¿ he added.

Last August, the FDA held up Zonagen¿s phentolamine-based drugs for sexual dysfunction, Vasomax and Vasofem, with a ¿not-approvable¿ letter, after a study showed some male rats developed a mysterious proliferation of brown fat, which is common to hibernating animals. Earlier this year, the company submitted new data from a two-year rat study, but the FDA said that still more information was required. (See BioWorld Today, May 18, 2000; and April 19, 2000.)

The firm reduced its staff by about one-third in September.

¿We¿re down to about 13 full-time employees,¿ Ploth said. ¿[The FDA] put us on clinical hold [first], and now we¿re on partial clinical hold,¿ which means trials that last no longer than 12 weeks may be conducted. In the UK, a clinical hold ordered earlier has been lifted, he said.

Vasomax is an immediate-release oral formulation of phentolamine mesylate, which is a short-term alpha-adrenergic receptor blocker that stimulates smooth muscle relaxation and causes vasodilation. Approved decades ago as a treatment for hypertension and used more recently in diagnosing adrenal tumors, phentolamine recently has been used off-label for erectile dysfunction. Vasofem is a similar formulation of the drug, in development for female sexual dysfunction.

Zonagen¿s stock (NASDAQ:ZONA) closed Wednesday at $2.50, up 25 cents.