Chelsea Therapeutics (Nasdaq: CHTP), regrouping from orphan drug Northera’s failure to secure regulatory approval, now plans to resubmit a new drug application in early 2013 with data from a modified phase 3 study.

The Charlotte-based drug developer announced the plans following its meeting with the U.S. Food and Drug Administration to discuss the complete response letter received in March for Northera, a compound developed to treat dizziness and fainting in Parkinson’s disease patients.

The company initially said that it understood the FDA’s concerns were about the drug’s durability — how long its effect lasts over a two- to three-month period. But Chelsea said that after subsequent discussions with the agency, it was clearer that the FDA was concerned that most of the data submitted in the drug application came from one study site, which “mitigated the persuasiveness of that study and prevented the FDA from accepting Study 301 alone as adequate evidence of effectiveness.”

Northera was developed to treat neurogenic orthostatic hypotension, or NOH, a condition in which patients experience dizziness and fainting upon standing due to low blood pressure. Though rare, NOH can be found in patients with Parkinson’s disease, multiple systems atrophy and pure autonomic failure. Patients who have NOH have few treatment options. Shire‘s (NASDAQ:SHPGY) ProAmatine, currently the only FDA-approved NOH treatment, has a black box warning and Shire must conduct additional studies to confirm the drug’s clinical benefit.

Chelsea’s Northera was already in another late-stage trial, Study 306B, studying the compound’s effect preventing falls in Parkinson’s patients with NOH. Chelsea now plans to change the endpoint of that study to evaluate orthostatic hypotension symptoms. The study will also increase in size from about 160 to 200.

The FDA still has to review Chelsea’s proposal. But the company said that it had “meaningful discussions” with the agency about using data from Study 306B. The study currently has 161 patients enrolled. Chelsea expects to complete enrollment in the fourth quarter, which would allow the company to get initial data to resubmit a drug application in the first quarter of 2013. A regulatory decision could come six months later.