German drugs and pesticides maker Bayer AG will stop selling a type of medicine to treat multiple sclerosis in mid-2016 due to "supply problems," a government-backed charity warned.

The drug maker confirmed that it will stop selling the drug, known by its trade name Betaferon, in the domestic market in August. It was tight-lipped about why it plans to cut supplies in China.

The China Charity Federation, a non-profit organization funded by the Ministry of Civil Affairs, posted a statement on the looming supply cut on their website on January 18.

Multiple sclerosis (MS) is a rare neurological disease in which the protective layer around nerve fibers in the brain and spinal cord – known as myelin – becomes damaged. If this damage is not controlled, it can result in permanent disability.

Data from the China Food and Drug Administration (CFDA) show that the regulator has only approved two medicines to treat MS: Betaferon and Rebif, a drug manufactured by German pharmaceutical giant Merck KGaA. The patent for Rebif in the country expired in 2013.

Several MS patients told Caixin that Betaferon was the most widely available treatment since then.

On average, patients require a dose of the medicine to be injected every other day, throughout their lifetime. Each shot costs 850 yuan, and a patient has to spend around 153,000 yuan each year for the treatment, patients said.

In 2012, China Charity Federation and Bayer started giving free injections needed for either four or six months of treatment for a patient based on their income every year. The project's website, however, shows that only about 1,000 patients applied for this program in the past four years.

The project stopped accepting applications on March 1.

Most patients cannot get regular treatment due to the high cost of medicine, said one patient who asked not to be named. There are only a handful of outdated surveys to gauge how many suffer from the disease. Some experts estimated that there were around 13,000 to 26,000 MS patients in 2009, the latest year for which data is available.

The global sale of Betaferon dropped 8.1 percent in 2015 from the previous year, according to the company's annual report.

The CFDA has not issued any statement on what the government plans to do once supplies run out.

(Rewritten by Chen Na)