Baxter and CTI Biopharma have moved a step closer to bringing their myelofibrosis candidate pacritinib to market after reporting positive results in a phase III trial.
Pacritinib is a novel oral JAK2/FLT3 inhibitor and if approved would compete directly with Incyte and Novartis’ Jakafi (ruxolitinib) in myelofibrosis, a chronic malignant bone marrow disorder. Baxter licensed rights to pacritinib from CTI in 2013 in a deal valued at up to $272m deal.
In the PERSIST-1 trial, pacritinib achieved the primary objective of being more likely to achieve a clinically significant 35% or greater reduction in spleen volume when compared to best-available therapy, not including Jakafi.
CTI believes that pacritinib may offer an advantage over other JAK2 inhibitors such as Jakafi by providing better disease and symptom control without the need for dose titration to prevent treatment-related reductions in platelet and red blood cell counts, a recognised side effect of Incyte and Novartis’ drug.
Importantly, in PERSIST-1 pacritinib was able to achieve the desired reduction in spleen volumes regardless of the platelet counts of patients when they were first enrolled into the trial. A number of patients with severely low platelet counts – known as thrombocytopenia – were included in the patient population, according to the company.
A clearer picture of the competitive profile of pacritinib versus Jakafi will come when the results of Baxter and CTI’s second phase III study – PERSIST-2 – are reported later this year. The trial will also compare pacritinib to best available therapy, but in this case that will include JAK2 inhibitors.
Sales of Jakafi are already running in excess of $500m a year, with Incyte reporting sales of $358m in 2014 and Novartis – which sells its as Jakavi outside the US – recording revenues of $279m for the drug.
The recent approval of Jakafi in a new indication – the rare blood cancer polycythemia vera (PV) – is expected to drive sales above the $1bn mark, with additional upside if it proves effective in solid tumours such as pancreatic cancer, according to analysts.
Meanwhile, the FDA has awarded pacritinib fast-track status for the treatment of myelofibrosis, including those with low platelet counts and those who are not responding to or tolerating current JAK2-targeting therapies. Assuming positive results in both PERSIST trials CTI has predicted it could be in a position to file for approval of pacritinib later this year or early in 2016.
Other JAK2 inhibitors coming through the pipeline for myelofibrosis include Gilead Sciences’ CYT387, which it acquired as part of its $510m takeover of YM Biosciences at the end of 2012.