No pharmaceutical companies were interested in selling the drug because hairy cell leukemia was an orphan disease, so Beutlers lab synthesised and packaged it and supplied it to the hospital pharmacy; the laboratory also developed a test to monitor blood levels. This was the first treatment that led to prolonged remission of hairy cell leukemia, which was previously untreatable. : 14–15 In February 1991, Scripps began a collaboration with Johnson & Johnson to bring intravenous cladribine to market, and by December of that year, Johnson & Johnson had filed a new drug application; cladribine was approved by the FDA in 1993 for hairy cell leukemia as an orphan drug, and was approved in Europe later that year. : 2 The subcutaneous formulation was developed in Switzerland in the early 1990s and it was commercialised by Lipomed GmbH in the 2000s. : 2

Safety profile of cladribine in hairy cell leukemia
Injectable cladribine suppresses the bodys ability to make new lymphocytes, natural killer cells, and neutrophils (called myelosuppression); data from hairy cell leukemia studies showed that about 70% of people taking the drug developed dangerously  low levels of white blood cells and about 30% developed infections and some of those progressed to septic shock; about 40% of people taking the drug had fewer red blood cells and became severely anaemic; and about 10% of people had too few platelets. At the dosage used to treat hairy cell leukemia in two clinical trials, 16% of people had rashes and 22% had nausea, the nausea generally did not lead to vomiting.
A meta-analysis of data from clinical trials comparing the risk of cancer and other disease-modifying therapies showed that cladribine tablets did not increase the risk of cancer at the doses used in the initial clinical trials.Based on the supporting data from the completed clinical trials that confirmed no increased risk of cancer, Merck announced it would again seek regulatory approval. In 2016, the EMA accepted its application for review. On June 22, 2017, the EMAs Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion, recommending the granting of a marketing authorisation for the treatment of relapsing forms of multiple sclerosis.Cladribine tablets were later approved in Europe, in August 2017, for highly active relapsing-remitting multiple sclerosis, and has since been approved by the FDA for the treatment of relapsing-remitting and secondary progressive multiple sclerosis in the US. Use in multiple sclerosis
As per the EU label, cladribine tablets are indicated for the treatment of adult patients with highly active relapsing multiple sclerosis as defined by clinical or imaging features: (i) patients with a relapse in the previous year and at least one T1 Gd+ lesion or 9 or more T2 lesions, while on another disease-modifying therapies or (ii) patients with two or more relapses in the previous year, whether on disease-modifying treatment or not.Two main approaches to multiple sclerosis treatment maintenance therapy are used – immunomodulation and immunosuppression and alternatively, immune reconstitution therapy. Classified as the latter, cladribine tablets are administered intermittently as a short treatment course without continuous immunosuppression.