The National Institute for Health and Care Excellence has issued draft guidelines backing restricted use of Pfizer’s Mylotarg for newly diagnosed acute myeloid leukaemia (AML), but has asked for more information on the firm’s Besponsa for a type of acute lymphoblastic leukaemia (ALL).

Mylotarg (gemtuzumab ozogamicin) is a targeted therapy consisting of an antibody connected to an anti-tumor agent that is toxic to cells, and thought to work by taking the anti-tumour agent to the AML cells that express the CD33 antigen, blocking the growth of cancerous cells and causing cell death.

Mylotarg was approved last month after clinical trials showed 81 percent of patients treated with the drug reached remission, while study results show that the drug in combination with chemotherapy offers a statistically significant and meaningful improvement in median event-free survival versus chemotherapy alone (17.3 months and 9.5 months, respectively).

NICE has endorsed Mylotarg’s use only in patients with the disease that has favourable or unknown cytogenetics, which can help predict treatment response.

The draft guidance does not recommend Mylotarg for people whose disease has intermediate cytogenetic status, meaning that around 65 percent of the eligible patient population are currently excluded from the provisional recommendation.

Further, the guidance states that the committee could not make recommendations for people with unknown cytogenetics where there is an urgent need to start treatment before the cytogenetic test results are available, despite acknowledging that in clinical practice patients would begin treatment whilst awaiting the cytogenetic test results, Pfizer said, adding that it would provide further info to the cost regulator.

“We are pleased that NICE has recognised the important impact that gemtuzumab ozogamicin could have on people diagnosed with acute myeloid leukaemia in the UK, and we welcome today’s preliminary decision to recommend the medicine for patients with favourable or unknown cytogenetics,” said Craig Eagle, head of Oncology, Pfizer UK.

“However, this provisional recommendation currently excludes 65 percent of the eligible patient population and so we will continue working with NICE to help ensure that all patients who are eligible to benefit from this treatment are able to access it once a final recommendation is issued.”

Elsewhere, the Institute has requested further evidence on the use of Besponsa (inotuzumab ozogamicin) for treating relapsed or refractory CD22-positive B-cell precursor ALL in adults.

While evidence shows that the drug boosted the rate of stem cell transplant, NICE has asked Pfizer to revise its economic models with several new assumptions, including updating evidence on the number of days a person may need to spend in the hospital during treatment.

The Institute is currently reassessing the evidence on Besponsa after rejecting the drug in draft guidelines last year, having concluded that evidence from clinical trials showed no survival benefit from the drug compared to current treatment.