Previous studies of gemtuzumab ozogamicin (Mylotarg) had variable results in acute myeloid leukemia (AML). Before trials reported at the 2011 ASH Annual Meeting, two major studies had compared chemotherapy with or without gemtuzumab in patients with AML, said Martin Tallman, MD, Chief of the Leukemia Service at Memorial Sloan-Kettering Cancer Center, New York. One study from the Medical Research Council in London, showed a benefit of gemtuzumab in favorable-risk patients only,¹ while the second study, from the Southwest Oncology Group (SWOG), showed increased toxicity and greater mortality with no significant benefit for gemtuzumab.²

In 2010, gemtuzumab was withdrawn from the market in the United States due to reports of fatal toxicity in the SWOG trial. “This drug is not available and no one is using it,” Dr. Tallman said. “Here comes this study by the French showing a benefit in event-free survival and disease-free survival in patients with generally favorable and intermediate risk.³ The curves look impressive.”

Dr. Tallman explained that the standard of treatment for AML (ie, daunorubicin and cytaraine) hasn’t changed in 4 decades. “I think this study has the potential to change the standard of care,” he said.

If this study proves to be practice-changing, there will be tremendous pressure on Pfizer to resubmit an application for approval for gemtuzumab, Dr. Tallman predicted. A Pfizer spokesperson said that the results of the French study and another positive study in older patients with AML also presented at the ASH meeting⁴ are currently being reviewed, and a decision will be made as to whether to go forward with a new submission to FDA. ■

Disclosure: Dr. Tallman reported no potential conflicts of interest.

References

1. Burnett AK, Hills RK, Milligan D, et al: Identification of patients with acute myeloblastic leukemia who benefit from the addition of gemtuzumab ozogamicin: results of the MRC AML15 trial. J Clin Oncol 29:369-377, 2010.

2. Petersdorf S, Kopecky K, Stuart RK, et al: Preliminary results of Southwest Oncology Group study S0106: An international intergroup phase 3 randomized trial comparing the addition of gemtuzumab ozogamicin to standard induction therapy versus standard induction therapy followed by a second randomization to post-consolidation gemtuzumab ozogamicin versus no additional therapy for previously untreated acute myeloid leukemia. Blood (ASH Annual Meeting Abstracts) 114:Abstract 790, 2009.

3. Castaigne S, Pautas C, Terre C, et al: Fractionated doses of gemtuzumab ozogamicin (GO) combined with standard chemotherapy improves event-free survival in newly-diagnosed de novo AML patients aged 50-70 years old: A prospective randomized phase 3 trial from the Acute Leukemia French Association (ALFA). 53rd Annual Meeting of the American Society of Hematology. Abstract 6. Presented December 11, 2011.

4. Burnett AK, Hills RK, Hunter AE, et al: The addition of gemtuzumab ozogamicin to intenstive therapy in older patients with AML produces a significant improvement in overall survival: Results of the UK NCRI AML 16 randomized trial. 53rd Annual Meeting of the American Society of Hematology. Abstract 582. Presented December 12, 2011.