* Drug will compete with Allergan's treatment
* Plans to file marketing application in 2019
* Shares fall as much as 33 pct to hit all-time low (Adds CEO quote from conf. call, analysts comments; updates shares)
March 26 (Reuters) - Biohaven Pharmaceutical Holding said its treatment for acute migraine cleared two late-stage studies, but investors worried about its commercial viability as the efficacy data failed to distinguish from Allergan's rival treatment.
Shares plunged as much as 33 percent to touch a record low of $16.51 in early trading on Monday.
In February, Allergan reported strong efficacy data for its migraine treatment, ubrogepant.
A late entrant to the competitive arena of migraine treatments, Connecticut-based Biohaven's rimegepant is part of a new class of medicines called CGRP receptor antagonists.
Analysts said data from Biohaven's studies showed the oral drug is much safer than Allergan's. However, comparing the efficacy of the two drugs is complicated given the differences in placebo rates and an extra dose given after two hours in Allergan's trial.
"The bad news is that the efficacy profile will be debated given the limited 2 hour effect and is likely to lead investors to discount the commercial potential," Morgan Stanley analyst Matthew Harrison said in a client note.
The company highlighted the treatment's strong safety profile and noted that the lack of a second "rescue" dose would be a key selling point with patients and insurers.
"We have the dosing correct ... patients do not need to chase it with another second dose, they don't need to chase it with other rescue meds," Biohaven's Chief Executive officer Vladimir Coric said in a conference call with analysts.
RACE FOR CGRP Biohaven, which went public in May, is one of several drugmakers looking for a slice of migraine market that is expected to swell to more than $10 billion in 2025 from $3 billion in 2015 in the United States and other developed countries.
Companies including Amgen Inc, Teva, Eli Lilly and Alder Biopharmaceuticals are in a race to be the first to come out with a drug for a condition that affects 39 million people in the United States.
Given the likely primary care market where these new therapies will be marketed, William Blair's analyst Tim Lugo said rimegepant's impressive clean safety profile could be a strong differentiator versus Allergan's treatment.
Biohaven, which is also developing treatments for obsessive compulsive disorder and Alzheimer's disease, said it plans to file marketing application for its migraine treatment in 2019.
(Reporting by Tamara Mathias in Bengaluru, Additional reporting Anuron Kumar Mitra; Editing by Arun Koyyur)