(Corrects executive title in paragraph 7 to co-founding managing director, not founding managing director, after company clarifies)

Feb 14 (Reuters) - Latigo Biotherapeutics emerged from stealth mode on Wednesday and said it had raised $135 million in series A funding to advance clinical trials of its non-opioid pain treatments, including a drug that is being tested in healthy volunteers.

Westlake Village BioPartners, the venture capital (VC) firm that founded Latigo, led the funding round. Two other healthcare and life-sciences focused VCs — 5AM Ventures and Foresite Capital — were co-leads.

The Thousand Oaks, California-based company did not disclose the valuation at which the funds were raised.

The round fetches a rare big check in an early stage fundraise, where the deal size is typically much smaller. Last year, early stage funding rounds fetched less than $20 million on average, data from PitchBook showed.

"This is not your typical series A these days. The funding really speaks to the commitment of the investors, and to this space," said Nancy Stagliano, chair of Latigo's board.

Latigo's lead drug, LTG-001, is being tested in an early stage trial. The drug, intended to treat acute and chronic pain, belongs to the same class of medicines as a therapy by Vertex Pharmaceuticals that reduced acute pain in a late-stage study last week.

"There's been very little investment and very little real innovation in this space. For Vertex ... to provide proof-of-concept now is huge for the field," said Sean Harper, co-founding managing director for WestLake.

But "many times, the first-in-class molecule doesn't end up being the dominant best-in-class drug on the market," Harper said, adding that there was room for competitors in the still-nascent market.

Latigo's lead drug and Vertex's treatment target a protein called Nav1.8 in an attempt to block pain at its source. Opioids trigger the brain's reward center as they travel through blood, leading to the potential for addiction and abuse. (Reporting by Manas Mishra and Niket Nishant in Bengaluru; Editing by Shilpi Majumdar)