By Jim Shrine

Palatin Technologies Inc. and Nihon Medi-Physics Co. Ltd. changed the focus of their collaboration, in a move that will expand potential targets based on Palatin's metal ion-induced distinctive array of structures (MIDAS) peptide technology.

The companies ended a collaboration begun in late 1996, and signed a letter of intent that contemplates development of diagnostic and therapeutic radiopharmaceutical products based on MIDAS, which uses metal ions to stabilize and enhance the activity of peptides.

Palatin, of Princeton, N.J., and Nihon, of Tokyo, were exploring the use of MIDAS to develop an infection imaging agent, using targets selected by Nihon.

"We worked with them to develop stable peptides that would bind to the proposed targets," said Charles Putnam, Palatin's executive vice-president and chief operating officer. "We were successful doing that, but our feeling at this time is those targets will not yield the level of performance that merits clinical development.

"The technology worked well," Putnam told BioWorld Today, "and now we will redirect that technology. We're setting aside development of an infection imaging agent and going to look at a number of diagnostic and therapeutic targets."

Potential therapeutic targets include cancers common in Japan, such as lung and stomach cancers, said Edward Quilty, Palatin's chairman, president and CEO.

The first phase of the new collaboration will entail identifying target receptors, which is expected to take three to six months. The deal is expected to include an up-front payment to Palatin as well as potential milestones.

Putnam said the reworked and extended collaboration "continues to suggest there is merit in that technology."

MIDAS allows researchers to manipulate the metal ion backbone and various amino acid chains, leading to the use of structural information about a receptor to design a peptide sequence that will mate with a receptor.

"It's really a rational design process," Putnam said. "We were quite successful developing high-affinity receptor-binding compounds, and developing them very quickly."

Palatin is in the process of raising money in a private placement to shore up its financial position, which on Sept. 30 showed cash of $3.4 million. The deal with Nihon covers development costs, may lead to milestones and is reassuring to investors, showing that a major player in the radiopharmaceutical field continues to stand behind the technology, Putnam said.

Lead Product Now At Phase III

Palatin's lead product is LeuTech, a murine antibody conjugated with technetium that binds to white blood cells. It is designed to produce diagnostic images quicker, safer and more cost-effectively than current labeling techniques, Putnam said. LeuTech is in Phase III studies for diagnosing occult infections, specifically equivocal appendicitis.

The company plans to broaden applications of LeuTech to include hidden infections in areas such as osteomyelitis, fever of unknown origin, post-surgical infections and inflammatory bowel disease. The ongoing study is expected to be completed in the first quarter, Putnam said, with a license application targeted toward the middle of 1999.

Another product, PT-14, is an injectable peptide being developed to alleviate sexual dysfunction. The company also is working to develop an oral formulation. The product was licensed from the University of Arizona.

Physician-sponsored studies of PT-14 are ongoing and Palatin hopes to take an oral product into the clinic in the second half of next year. That product was not developed using MIDAS.

PT-5, however, is a MIDAS molecule - a somatostatin analogue, conjugated with rhenium, that is expected to be developed for cancer imaging and possibly diagnostic applications. A Phase I/II study in Germany is testing the product's therapeutic potential in metastatic cancers, Putnam said.

Originally, the plan at Palatin was to in-license products, such as was done successfully with PT-14, he added. "But our growth is more likely to come from internal development of targeted peptides," Putnam said. "A great deal can be done with melanocortin receptors and other families of molecules to which the MIDAS concept can be applied. We have several internal research projects to develop MIDAS-based peptides. I think it's likely we'll emphasize that in the near term, although we're open to in-licensing opportunities."

Palatin's stock (NASDAQ:PLTN) fell 25 cents Tuesday, closing at $4.062. n

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