Chong Kun Dang said it has obtained approval for Raparobell, a generic copy of Pfizer’s immunosuppressive agent Rapamune (ingredient: sirolimus), from the Ministry of Food and Drugs Safety.

Sirolimus is an immunosuppressive drug to prevent organ rejection in kidney transplant patients aged 13 or more. Renal transplantation is the last treatment for those who lost kidney functions due to diabetic nephropathy or pyelonephritis.

In kidney transplant surgeries, physicians must use an immunosuppressive drug to prevent rejection of a transplanted organ and to maintain the functions of the kidney. Patients who start to take an immunosuppressant should take the medication for a lifetime.

Pfizer’s Rapamune, which sold 2.2 billion won ($1.9 million) in 2017 according to IQVIA data, had its patent expired recently and industry watchers expected an outburst of generic drugs. However, Chong Kun Dang is the only drugmaker that gained access to the market.

Analysts said the reason only Chong Kun Dang entered the immunosuppressant market is that the market was too small. Rapamune sold only 2.2 billion won, despite its status as an original drug.

Usually, drugmakers aim to sell 1-5 billion won worth generic drugs. The small size of the original drug’s sales did not generate much appetite for local firms to develop generic drugs, observers said.

However, it was a different story for Chong Kun Dang, as it has already been selling other immunosuppressant drugs.

The drugmaker is selling Tacrobell (tacrolimus hydrate), a generic drug of Astellas Pharma’s Advagraf. The drug’s prescriptions amounted to 36.9 billion won last year, according to IQVIA data.

Chong Kun Dang’s another immunosuppressant My-Rept (mycophenolate mofetil) sold 10.3 billion won, closely chasing Roche’s treatment Cellcept that sold 14 billion won, last year.

Cipol-N, Chong Kun Dang’s generic drug of Novartis’ Sandimmun Neoral (cyclosporine), sold 18.7 billion won last year.

The combined sales of the three immunosuppressants reached 66 billion won last year. As Chong Kun Dang has accumulated some brand recognition through the sales of the three treatments, the company had enough reason to try a Rapamune generic market, observers said.

The pharmaceutical industry is paying attention to whether Chong Kun Dang will become a new leader in the immunosuppressant market with the release of a new generic drug.