Two Icagen (Nasdaq: ICGN) institutional investors opposed to Pfizer's (NYSE: PFE) $56 million offer for the pain-drug-development company now say Icagen's value should be nearly three times that amount.

Merlin Nexus and New Leaf Venture Partners say that with potential sales of pain-treatment products exceeding $2 billion a year, they value Durahm, N.C.-based Icagen at between $100 million and $165 million, or $11 to $19 per share. Pfizer's offer amounts to $6 per share. Before Pfizer's interest in Icagen became public in June, Icagen shares traded at around $2.40.

The Pfizer acquisition of Icagen, announced July 20, is expected to close by the end of the year. On July 28, Merlin Nexus and New Leaf sent a letter to Icagen's board of directors stating their belief that Pfizer's offer was inadequate and not in shareholders' best interests.

The two investors sent Icagen's board another letter on Aug. 11 reiterating their opposition to Pfizer's price and explaining how they value the company. Merlin Nexus and New Leaf claim their dollar estimates for Icagen's compounds are "conservative" and even assume that at least one of the company's three clinical programs will fail. Icagen's lead compound is set to enter mid-stage clinical trials as a potential treatment for pain and epilepsy.

But the two investors are most interested in the potential of an earlier-stage pain compound: PF-05089771. That compound is in phase 1 studies that Merlin Nexus and New Leaf say were supposed to be completed in March. Pfizer had spurned Icagen's suggestion of an acquisition four times before reaching out to the drug-development company in April with an offer.

"The timing suggests to us that the clinical data supporting the initial safety and efficacy of the Nav1.7 program may have been a driver behind this unexpected new interest in a transaction," Merlin Nexus and New Leaf said in their letter.

The two investors say data from that trial should be made public so shareholders can use the information to determine whether to tender their shares.

In its release of second-quarter financial results, Icagen acknowledged the compound referenced by Merlin Nexus and New Leaf. But Icagen said only that the phase 1 trial "is currently in progress." The company says nothing about any available data.

Medcitylogo