US regulators have issued a green light for Johnson & Johnson/Pharmacyclics 'breakthrough' drug Imbruvica as a single treatment for mantle cell lymphoma.

Specifically, Imbruvica (ibrutinib), an oral BTK inhibitor, has been approved by the Food and Drug Administration following a priority review for use in patients who have received at least one prior therapy, after clinical trials showed a 65.8% overall response rate in this subset.

Further data from the pivotal 111-patient trail showed that 17% of patients with the rare blood cancer achieved a complete response and 49% a partial one, while median duration of response was 17.5 months.

On the safety side, treatment-emergent grade 3 or 4 cytopenias (adverse reactions and laboratory abnormalities combined) were reported in 41% of patients, while warnings in the prescribing information include haemorrhage, infections, myelosuppression, renal toxicity, second primary malignancies and embryo-fetal toxicity.

According to lead investigator of the registration trial, Michael Wang at the University of Texas MD Anderson Cancer Center, the approval of Imbruvia marks "a meaningful day for previously treated mantle cell lymphoma patients, who are in need of new treatment options".

As per their 2011 agreement, Pharmacyclics and J&J's Janssen unit will co-commercialise the once-daily oral therapy in the USA, where it will compete with the only two other drugs approved for the condition, Millennium:The Takeda Oncology Company's Velcade (bortezomib; marketed by J&J outside the US) and Celgene's Revlimid (lenalidomide). 

'Breakthrough' process

Imbruvica is one of the first treatments to receive FDA approval via the Breakthrough Therapy Designation (BTD) pathway, which is intended to speed up the development and review time for a potential new medicine. 

The drug has actually already bagged three BTDs from the FDA: as a monotherapy for the treatment of: patients with chronic lymphocytic leukaemia/small lymphocytic leukaemia with a particular genetic defect, patients with relapsed/refractory MCL who have received prior therapy and patients with Waldenström’s macroglobulinemia.

Some analysts are forecasting that sales of Imbruvica could hit $4 billion by 2019 if it is approved across its proposed indications.