endpoint was determination of the MSSD. This analysis reports results for the long term safety
and other secondary and exploratory endpoints.
Results: Of 69 enrolled patients, 38 received ruxolitinib at the MSSD of 10 mg bid (S1, n=20;
S2, n=18) and are the focus of this analysis. Baseline characteristics were indicative of
advanced disease in both strata.
The most frequently reported adverse events (AEs) included thrombocytopenia (S1, 50%; S2,
78%) and anaemia (S1, 55%; S2, 44%); other frequent AEs included diarrhoea, ecchymosis,
decreased platelet count, and pyrexia (each reported in 30% of patients) in S1, and cough
(33%) in S2. Thrombocytopenia was the most common AE leading to discontinuation (S1, 1
patient; S2, 4 patients). The most common grade ≥3 AEs reported included thrombocytopenia
(S1, 40%; S2, 78%) and anaemia (S1, 25%; S2, 17%). Four on-treatment deaths occurred during
the study, 2 in each stratum; one of these (S1, cardiac arrest) was assessed as related to the
study drug.
Overall, 40% (6/15) and 38% (3/8) of evaluable patients in S1 and S2 achieved a spleen
response (defined as ≥50% reduction in spleen length from baseline) at week 24; 33% (5/15)
and 30% (3/10) of evaluable patients in S1 and S2 achieved a spleen response at week 48,
while 55% (11/20) and 67% (12/18) of evaluable patients in S1 and S2 achieved a spleen
response at any time during the study. A symptom response (defined as ≥50% reduction in
MF-SAF TSS from baseline to week 24) was observed in 31% (4/13) and 40% (4/10) of
evaluable patients in S1 and S2, respectively.
Conclusions: Results confirm the suitability of a 10 mg bid starting dose of ruxolitinib in
patients with MF and low platelet count at baseline. The AEs observed were consistent with
the known safety profile of ruxolitinib, with no new or unexpected AEs reported, even in
patients with more severe disease. A substantial proportion of patients experienced
treatment benefits at this dose, including spleen length reduction and symptom
improvement.