Flex Pharma Completes Enrollment of Human Proof of Concept Efficacy Study in Nocturnal Leg Cramps

July 26, 2016

Boston, MA – Flex Pharma, Inc. (NASDAQ: FLKS) today announced that it has completed enrollment of its human proof-of-concept efficacy study in nocturnal leg cramps (NLC) with its chemically synthesized, single molecule, transient receptor potential (TRP) ion channel activator, formulated as an orally disintegrating tablet. Subject enrollment for this study initiated in late May and completed ahead of plan. This randomized, blinded, controlled, cross-over study is designed to evaluate the safety and efficacy of its single agent in over 50 subjects who suffer from frequent nocturnal leg cramps. Topline results are expected by year end.

Nocturnal leg cramps can cause severe pain, interrupted sleep, reduced quality of life and can interfere with activities of daily living. The Company estimates that NLC affects over four million Americans nightly. There is no approved therapeutic in the United States to treat this condition.

“The rapid enrollment into this study underscores the substantial unmet need for a therapeutic agent for people who suffer from frequent leg cramps at night,” said Flex Pharma Chief Medical Officer Thomas Wessel, M.D., Ph.D., who served as the medical lead for three products approved in United States: Razadyne®, Lunesta® and Ampyra®. “Given the underlying mechanism of alpha motor neuron hyperexcitablity in cramps and spasms, we have also initiated a Phase 2 study with our single agent for patients with MS, and we expect to begin our Phase 2 study in ALS patients later this year.” These studies in MS and ALS will be conducted outside the U.S.

“Flex Pharma’s agent is the leading clinical candidate for NLC and I am hopeful that their efforts will ultimately help the millions of people who suffer from this painful condition and currently have no safe and effective therapeutic options,” noted John Winkelman, M.D., Ph.D., Chief of the Sleep Disorders Clinical Research Program at Massachusetts General Hospital and Flex Pharma Scientific Advisory Board member, who was involved in the clinical development of both Requip® and Mirapex®, approved agents for restless legs syndrome (RLS).

The current study builds upon a completed, successful, randomized, controlled, blinded cross-over study (n=50), in which the Company’s extract formulation demonstrated statistically significant positive human efficacy on the key endpoints. Results from that study were accepted and presented as a late-breaker at the American Academy of Neurology Annual Meeting in April 2016.

About Flex Pharma

Flex Pharma, Inc. is a biotechnology company that is developing innovative and proprietary treatments for nocturnal leg cramps, cramps and spasms associated with severe neuromuscular conditions such as MS and ALS, and exercise-associated muscle cramps. Flex Pharma was founded by National Academy of Science members Rod MacKinnon, M.D. (2003 Nobel Laureate), and Bruce Bean, Ph.D., recognized leaders in the fields of ion channels and neurobiology, along with Chair and CEO Christoph Westphal, M.D., Ph.D.

Visit www.TeamHOTSHOT.com for updates and to learn more about HOTSHOT™, the Company’s consumer product which is scientifically proven to prevent and treat muscle cramps.

HOTSHOT is a consumer product that is marketed to endurance athletes for exercise-associated muscle cramps. HOTSHOT complements the Company’s drug development business and is not intended to diagnose, treat, cure or prevent any disease.

Follow Flex Pharma (@flexpharma) and HOTSHOTTM( @Team_HOTSHOT) on Twitter

Cautionary Note on Forward-Looking Statements
This press release contains forward-looking statements for purposes of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. We may, in some cases, use terms such as “predicts,” “believes,” “potential,” “proposed,” “continue,” “estimates,” “anticipates,” “expects,” “plans,” “intends,” “may,” “could,” “might,” “will,” “should” or other words that convey uncertainty of future events or outcomes to identify these forward-looking statements. Forward-looking statements include statements regarding our intentions, beliefs, projections, outlook, analyses or current expectations concerning, among other things: our expectations regarding studies of our current product candidates, including the success and timing of these studies; our beliefs regarding the potential benefits of our current product candidates; and expectations regarding the number of individuals that may suffer from nocturnal leg cramps. These forward-looking statements are based on management’s expectations and assumptions as of the date of this press release and are subject to numerous risks and uncertainties, which could cause actual results to differ materially from those expressed or implied by such statements. These risks and uncertainties include, without limitation: the status, timing, costs, results and interpretations of our clinical studies; the uncertainties inherent in conducting clinical studies, including receiving regulatory approval to conduct these studies; the fact that we rely on third parties to manufacture and conduct the clinical studies of our product candidates, which could delay or limit future development or regulatory approval; results from ongoing and planned preclinical development; expectations of our ability to make regulatory filings and obtain and maintain regulatory approvals; results of early clinical studies as indicative of results of future trials; the inherent uncertainties associated with intellectual property; and other factors discussed in greater detail under the heading “Risk Factors” in our Annual Report on Form 10-K for the year ended December 31, 2015 and subsequent filings with the Securities and Exchange Commission (SEC). You are encouraged to read Flex Pharma’s filings with the SEC, available at www.sec.gov, for a discussion of these and other risks and uncertainties. Any forward-looking statements that we make in this press release speak only as of the date of this press release. We assume no obligation to update our forward-looking statements whether as a result of new information, future events or otherwise, after the date of this press release.