Chelsea Therapeutics‘ (Nasdaq: CHTP) rheumatoid arthritis treatment failed in phase 2 clinical trials, leaving the beleaguered drug developer to focus its remaining resources on an orphan drug candidate that has already fallen short of regulatory approval.

The experimental rheumatoid arthritis drug CH-4051 demonstrated some effect on patients but did not prove better than existing rheumatoid arthritis treatment methotrexate. In fact, the methotrexate proved to work too well in the trial.

Simon Pedder, CEO of the Charlotte-based company, said the Chelsea compound’s results were impacted by the “unexpectedly robust response” reported by patients treated with methotrexate.

Chelsea believes higher doses of CH-4051 could treat rheumatoid arthritis and other inflammatory and autoimmune conditions. But Pedder said the company’s resources would be “better allocated” toward completing studies of Northera, a compound that has experienced its own difficulties. The orphan drug candidate was developed as a treatment for neurogenic orthostatic hypotension, or NOH, a rare condition that causes dizziness and fainting in patients who have Parkinson’s disease, multiple systems atrophy and pure autonomic failure.

Northera failed in March to secure U.S. Food and Drug Administration approval. But even before the FDA’s complete response letter, Chelsea had been conducting a phase 3 study of Northera’s effect preventing falls in Parkinson’s disease patients. Now Chelsea hopes modifying that phase 3 trial will be enough to support another new drug application in 2013. The company is expanding the trial’s enrollment and changing the primary endpoint from fall prevention to evaluate instead the compound’s effect on NOH symptoms.

The FDA has not yet signed off on this new study, though Chelsea’s meeting with the agency led the company to believe this study would be sufficient to support a new Northera filing. Chelsea can’t afford to wait. The company finished the first quarter with $15.7 million in cash – enough to last until through the second quarter of 2013.

Pedder had said Chelsea planned to find a drug partner for late-stage clinical development and commercialization of the company’s rheumatoid arthritis compound. A partnership could have infused Chelsea with some much needed cash. CH-4051′s phase 2 failure dashes those plans. For Chelsea, everything now rides entirely on Northera and the outcome of its revamped phase 3 trial.