A drug used to treat chronic myelogenous leukemia (CML) was successful in a large group of patients, proving that the Food and Drug Administration's (FDA) early confidence in the drug was justified, said a report in the Feb. 28 issue of the New England Journal of Medicine (Vol. 346, No. 9: 645-652).

Hagop Kantarjian, MD, and his colleagues reported on the continued benefit of Gleevec, also referred to as imatinib, in this patient group.

In December 1999, Brian Druker, MD, reported to the American Society of Hematology meeting on his work with the drug STI571, later to be called Gleevec. The drug was designed to target a molecular problem in the leukemia cells of patients with CML.

Only 83 patients were treated, but the responses were so complete and the side effects so few, that it became clear this was a profound new drug.

By May of 2001, the evidence of its benefit was so convincing that the FDA approved it for widespread use in patients with CML. This approval was one of the fastest ever given to any drug.

CML is diagnosed in over 4,000 people each year. This cancer carries the Philadelphia chromosome (located in cells). It produces the molecule leading to the leukemia. Gleevec targets this molecule and blocks its activity.

Most people can live several years with the disease, but eventually it changes to an acute leukemia that is resistant to most treatments and is often quickly fatal.

The researchers gave Gleevec to 454 people with CML still in the chronic phase who had failed previous treatment with interferon. Interferon has been the most successful drug used to treat CML until now.

In 95% of the patients, the leukemia disappeared from the blood. In over 40% of them, the Philadelphia chromosome-containing cells completely disappeared. No drug has ever been this successful in getting rid of this problem.

By the end of two years, almost 90% of the patients remains in remission. In those whose Philadelphia chromosome went away, it remains absent in 85%.

Some people had their cancer come back, and at least nine people have died of their leukemia. This is considered a low number since they had all failed treatment with interferon.

Gleevec, made by Novartis, is given as a pill. It has few major side effects compared to the previous standard treatment, interferon. Typical side effects were mild swelling, rashes, nausea, and muscle cramps. The drug was stopped in 11 patients (2.1%) because of side effects.

It is too early to tell if Gleevec will cure patients with CML or even if it is truly better than previous treatments. So far more than 10% of patients treated with Gleevec have relapsed and the follow-up period is short.

Because of this, a new trial comparing Gleevec with interferon in newly diagnosed patients is in progress. More will follow until its true place in the treatment of CML is known.