Dr. Ted Burns offered a gentle warning to his fellow neurologists attending a meeting in Hawaii this week.

Patients with a rare neuromuscular disease are at risk because the old, inexpensive drug they take today -- the only drug that allows them to walk, breathe and remain independent -- might disappear next year. It will be replaced by a different version of the same drug, no more effective but costing hundreds of thousands of dollars.

That old drug, known as 3,4-Dap, has been used successfully for more than 30 years to treat patients with Lambert-Eaton Myasthenic Syndrome (LEMS) -- a rare, neuromuscular disease that causes progressive muscle weakness. The drug's cost: Free if obtained from Jacobus Pharmaceuticals, a privately held drug maker based in New Jersey that has donated the drug at no charge to patients for more than 20 years.

Other LEMS patients obtain 3,4-Dap from compounding pharmacies (which provide personalized medications for patients), generally at a cost of less than $5,000 per year.

Burns, a professor of neurology at the University of Virginia, treats a handful of LEMS patients who get their 3,4-Dap for free from Jacobus.

On Wednesday, Burns spoke at the annual meeting of the American Association of Neuromuscular and Electrodiagnostic Medicine, raising concerns the availability of 3,4-Dap could be cut off because of actions taken by Catalyst Pharmaceuticals  (CPRX , which he believes is emulating the controversial drug-pricing strategies of Valeant Pharmaceuticals (VRX and Turing Pharmaceuticals generating heated criticism from the public and politicians.

"My goal is to raise awareness," said Burns, in an interview before his trip to Hawaii to speak at the conference. "Doctors treating neuromuscular diseases don't spend a lot of time paying attention to stuff life drug pricing, so I'm trying to place it on their radar."

Catalyst is taking advantage of a loophole in U.S. law that allows companies to seek approval for old drugs currently in use to treat patients but lack formal marketing clearance from the Food and Drug Administration.

After obtaining official FDA approval, companies like Catalyst can control access to the drug and charge whatever they want. They can also seek to prevent the old, unapproved version of the drug from ever being prescribed again through market exclusivity provisions in federal drug laws.

This is what Catalyst has told investors it intends to do with Firdapse, its version of 3,4-Dap to treat LEMS patients. The only difference between Firdapse and 3,4-Dap is a small chemical modification that makes Firdapse stable at room temperature. 3,4-Dap needs to be refrigerated.

The active ingredient in both drugs is exactly the same. Both drugs must be taken three times per day. Clinical studies have shown both drugs improve muscle function and walking ability of LEMS patients. 

Catalyst hasn't announced pricing for Firdapse if it's approved next year. Analysts who cover the company believe Catalyst will set the price of Firdapse at approximately $200,000 per year, or in line with other drugs treating rare, orphan diseases.

LEMS is an orphan disease, so Catalyst could be granted seven years of market exclusivity for Firdapse. That would mean LEMS patients treated with 3,4-Dap today would no longer have access to the drug, including the free 3,4-Dap provided by  Jacobus. They'd be forced to switch to Firdapse at a far greater cost.

Marta Brodsky calls the shipment of 3,4-Dap she receives free from Jacobus every three months "the miracle drug which lets me live my life."

She's been taking 3,4-Dap three times a day since 2008 when she was diagnosed with LEMS. Before the drug, Brodsky says she couldn't walk or move her arms. She had trouble breathing. She couldn't work or take care of herself.

Almost from the first dose of 3,4-Dap, her muscle function and breathing improved. Her California life resumed almost to normal.

Now, however, Brodsky is afraid her supply of 3,4-Dap will be taken away if Catalyst secures approval of Firdapse. She doesn't want to switch drugs, fearful that the health insurance she pays for herself won't cover the higher drug cost. She's also worried about risk of side effects that might be caused by the change in Firdapse to make it shelf stable.

"I used to be married to a biotech executive, so I appreciate the costs involved with drug research and development. But what Catalyst is trying to do with Firdapse really sticks in my craw because they are completely piggybacking on 3,4-Dap," says Brodsky. "They have no concern at all for patient safety, it's only about the dollar with Catalyst."

Catalyst defends its Firdapse plans, arguing the drug is more convenient for LEMS patients than 3,4-Dap and its manufacturing capabilities will insure a stable supply. The higher price will generate revenue that the company will use to broaden Firdapse's use into additional, similar diseases and fund programs to identify and diagnose patients.

Financial assistance programs will ensure LEMS patients will be able to afford the higher cost of Firdapse, Catalyst says.

Dr. Don Sanders, a professor of neurology at Duke University Medical Center and a leading expert on LEMS, says Catalyst sounds too much like Martin Shkreli, the CEO of Turing Pharma, which acquired Daraprim, an old infectious disease drug, and raised the price from $13 per pill to $750. Intense public pressure later forced Turing to lower the price of Daraprim.

Sanders probably treats more LEMS patients than any other doctor in the country. His patients receive Jacobus-made 3,4-Dap for free.

"There is absolutely no justification for what Catalyst is doing with Firdapse," says Sanders. "It is hard for me to believe, given the recent interest shown by major political figures about the high cost of drugs, that there won't be some political reaction to it."

Jacobus is not sitting idle while Catalyst marches Firdapse towards FDA approval. With Sanders' help, Jacobus completed a successful phase III study confirming the efficacy and safety of 3,4-Dap in LEMS.

Full results from the study were also presented this week at the American Association of Neuromuscular and Electrodiagnostic Medicine meeting in Hawaii, as well as at the American Neurological Association annual meeting earlier this month.

Jacobus is an intensely private company which has no need for Wall Street. The company was founded by David Jacobus in 1977 and is now co-run by his daughter Laura Jacobus. They generally do not speak to the media, nor do they issue public statements about their regulatory plans for 3,4-Dap.

Until now.

"It is our intention to file for FDA approval," Laura Jacobus told me in response to a question about Jacobus' plans for 3,4-Dap in LEMS. If Jacobus can get 3,4-Dap approved, Catalyst's plans for Firdapse, including the huge price increase, might be derailed.

She would not say when the 3,4-Dap filing would be completed because she didn't want to tip off Catalyst, which has said publicly the Firdapse FDA application should be completed during the current quarter.

She added, "We are very confident on our end."

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.