Pacritinib Displays Safety Profile Similar to Best Available Therapy in Myelofibrosis

Naveen Pemmaraju, MD

In patients with myelofibrosis, including individuals with platelet counts lower than 50 × 10⁹/L, treatment with pacritinib (Vonjo) had a comparable or superior safety profile compared to best available therapy — including ruxolitinib (Jakafi), according to results presented at the 2022 American Society of Clinical Oncology (ASCO) Annual Meeting.¹

While JAK inhibitors remain a pillar in the myelofibrosis treatment paradigm, they have recently come under scrutiny for their toxicity. In an effort to find a drug for the patient population that is more tolerable, researchers recently analyzed pacritinib’s safety profile across two clinical trials: PERSIST-2 and PAC203.

“The safety analysis really tries to focus on these toxicities of interest for patients treated with pacritinib at 200 mg orally, twice daily and best available therapy, including ruxolitinib in the phase 2 and phase 3 studies,” said Naveen Pemmaraju, MD, study author and associate professor of Leukemia at The University of Texas MD Anderson Cancer Center, said while presenting the findings.

“Importantly, the aim of this analysis is to describe the safety profile of pacritinib 200 mg orally, including time on treatment.”

A total of 160 patients given pacritinib were included in the analysis (n = 106 from PERSIST and n = 54 from PAC203). Ninety-eight were in the best available therapy cohort, including 44 on ruxolitinib.

While data showed that there was a higher rate of adverse events for those on pacritinib (1570 per 100 patient-years at risk, compared to 903/100 patient-years at risk), the rate of fatal adverse events was lower. The incidence of bleeding or cardiac events was slightly lower for those given pacritinib compared to those given best available therapy (12/100 vs 22/100 patient-years at risk, respectively). There were no major adverse cardiac events in the pacritinib events, whereas there were 5 in the best available therapy group. Thrombosis was similar between the 2 arms.

Infection was more prevalent in the pacritinib cohort, but fungal and viral infections happened less frequently for these patients compared to the best available therapy cohort. Additionally herpes zoster reactivation occurred less frequently on the pacritinib arm than it did the best available therapy arm (0/11 patient-years vs 2.4/100 patient years, and 5.5/100 patient-years, in the pacritinib, best available therapy and ruxolitinib arms, respectively).

When it came to malignant neoplasms, there was a similar rate between the two arms, with a statistically significant lower risk of non-melanoma skin cancer in patients given pacritinib compared to best available therapy (3/100 patient-years, versus 7/100 patient-years, including 11/100 patient-years for those on ruxolitinib, respectively).

“In conclusion, in this novel, risk-adjusted analysis, this project demonstrated that the safety profile of pacritinib…is comparable to (best available therapy),” Pemmaraju said. “Pacritinib 200 mg may, indeed, represent a full-dose therapeutic option for patients with myelofibrosis, include for even those patients with (myelofibrosis) and thrombocytopenia.”

_Reference

_{Pemmaraju N, Scott BL, Savona MR, et al. Risk-adjusted safety analysis of pacritinib (PAC) in patients (pts) with myelofibrosis (MF). J Clin Oncol 40, 2022 (suppl 16; abstr 7058)}