* Deal set at 0.9951 OPKO share for each Prolor share
* Prolor shares up 14.2 pct at 24.1 shekels ($6.66
* Prolor's hGH-CTP has completed four clinical trials (Adds CEO quotes, details, share reaction)
TEL AVIV, April 24 (Reuters) - OPKO Health Inc will buy Israel-based biopharmaceutical company Prolor Biotech Inc in an all-stock deal valued at $480 million to expand its portfolio of specialty drugs.
Holders of Prolor common stock will receive 0.9951 shares of OPKO for each share of Prolor, the companies said on Wednesday.
The deal is valued at $7.00 per Prolor shares and is expected to close in the second half of 2013. It represents a 20 percent premium to Prolor's Tuesday close on Amex of $5.83.
Its shares in Tel Aviv were up 14.2 percent to 24.1 shekels ($6.66) in early trade.
Prolor's version of human growth hormone, hGH-CTP, has completed four clinical trials, including a Phase II trial in adults with growth hormone deficiency (GHD).
The trials showed hGH-CTP has the potential to reduce the required dosing frequency of human growth hormone from a standard of one injection per day to a single weekly injection.
The treatment demonstrated a good safety and tolerability profile in these clinical trials, the companies said. A Phase II trial in children with GHD is in progress and a Phase III trial in adults with GHD is planned to begin in the second quarter.
"This transaction is consistent with OPKO's stated objective of broadening our portfolio of market-transforming therapies in selected specialty markets," said Phillip Frost, OPKO's chief executive.
With Prolor's pipeline, OPKO will have four significant products in Phase III clinical development, Frost said. "Prolor's drug-product candidates for growth hormone deficiency, hemophilia, obesity and diabetes ... are highly valuable assets that will complement OPKO's strategy."
Barrington Research Associates acted as financial adviser to OPKO while Jefferies LLC advised Prolor. (Reporting by Tej Sapru in Bangalore; and Tova Cohen in Tel Aviv; Editing by Helen Massy-Beresford)