FILE PHOTO: Signage is seen outside of the Food and Drug Administration (FDA) headquarters in White Oak, Maryland, U.S., August 29, 2020. REUTERS/Andrew Kelly/File Photo

By Puyaan Singh and Kamal Choudhury

(Reuters) -The U.S. Food and Drug Administration has denied approval for PTC Therapeutics' oral medication for a rare genetic disorder with limited treatment options, the company said on Tuesday.

In its so-called Complete Response Letter, the FDA said the data did not provide substantial efficacy evidence for the drug, vatiquinone, in treating Friedreich's ataxia and that a separate study was needed before resubmitting the application.

At least three analysts said the regulator's rejection was not surprising and that expectations had been low heading into the decision.

PTC's shares reversed premarket losses to rise more than 8% in morning trading.

The FDA approved Sephience - PTC's oral therapy for a rare metabolic disorder called phenylketonuria - last month, potentially countering revenue declines due to regulatory scrutiny and competition from cheaper rivals for its top-selling muscular disorder therapies, Translarna and Emflaza.

"We see today's CRL as a clearing event since investors can now turn their focus to the Sephience launch," J.P.Morgan analysts said in a client note.

The company said it planned to meet with FDA officials to discuss potential next steps.

"We are of course disappointed by the FDA's decision to not approve vatiquinone," CEO Matthew Klein said, adding that the data till date demonstrated that the drug could be safe and effective for children and adults living with the disorder.

Friedreich's ataxia is a rare genetic disorder that causes progressive damage to the nervous system, often leading to difficulty in walking, speech problems and heart complications.

The disease tends to develop in children and teenagers and gradually worsens over time.

Vatiquinone did not meet its main goal of significantly reducing disease progression in a key late-stage trial that was part of the company's marketing application.

Currently, Biogen's Skyclarys remains the only FDA-approved treatment for Friedreich's ataxia.

(Reporting by Kamal Choudhury, Puyaan Singh and Mariam Sunny in Bengaluru; Editing by Pooja Desai and Sahal Muhammed)