Agent reduces fibrosis, improves platelet counts in MF
| Treatment group (n) | WHO fibrosis
response at any time |
CIA fibrosis
response at any time |
Platelet
improvement |
| PRM-151 QW (7) | 3 | 4 | 2 |
| PRM-151 Q4W (7) | 3 | 6 | 4 |
| PRM-151 QW + RUX (6) | 2 | 4 | 1 |
| PRM-151 Q4W + RUX (6) | 3 | 5 | 1 |
“The responses we saw with single-agent PRM-151, in particular, give us a lot of confidence that this drug is absolutely reversing fibrosis in the bone marrow,” Dr Trehu said. “And that is very nicely correlated with improvements in platelets, which are much harder to see in patients who are getting ruxolitinib because it’s a myelosuppressive agent.”
Dr Trehu added that these data suggest a monthly dose of PRM-151 is sufficient to treat MF patients, and there is a path forward for PRM-151 both alone and in combination with ruxolitinib.
Hemoglobin and spleen responses
The researchers also observed some improvements in hemoglobin levels and spleen size after treatment.
Of the 15 patients who had hemoglobin levels below 100 g/L at baseline, 3 met criteria for hemoglobin improvement. This included becoming transfusion independent, having a 50% reduction in the need for transfusion, or experiencing a 2 g/L increase in hemoglobin.
“Other patients had a nice trend toward hemoglobin improvement,” Dr Trehu noted.
Of the 20 patients with palpable spleen at baseline, reductions occurred in all but 1 patient. Four patients had a 50% or greater reduction in spleen size, but this response did not last beyond 12 weeks.
Adverse events
Forty-eight percent of patients (13/27) had at least 1 treatment-related adverse event (AE). Grade 1 AEs included diarrhea (n=3), fatigue (n=2), bruising at the infusion site (n=2), oral herpes (n=1), joint swelling (n=2), and headache (n=2). One patient had grade 2 oral herpes.
There were 5 serious AEs that were possibly treatment-related. Three events, from which patients recovered, were abdominal pain, sialadenitis, and pneumonia. The other 2 serious AEs were gastroenteritis and pneumonia, which resulted in death in an 85-year-old patient.
There were 2 deaths unrelated to treatment. One was due to pneumonia, and the other was a result of multi-organ failure and cardiac arrest. 
*Information in the abstract differs from that presented at the meeting.
