This site is intended for healthcare professionals only
This site is intended for healthcare professionals only
medwireNews: Extended follow-up of a phase 1b trial shows that responses to sutimlimab are maintained after more than a year of treatment in a subset of chronic immune thrombocytopenia (ITP) patients with an inadequate response to multiple previous therapies.
The selective complement pathway inhibitor, which works by binding to complement component (C)1s, also demonstrated “an acceptable safety profile,” presenting author Catherine Broome (MedStar Georgetown University Hospital, Washington, DC, USA) told delegates of the virtual 62nd American Society of Hematology Annual Meeting and Exposition.
“These results provide evidence for the role of complement in clinical heterogeneity of ITP and provide a strong rationale for further investigation of the potential therapeutic effects of anti-C1s in patients with ITP,” she added.
The study enrolled 12 patients with severe (platelet count ≤30 x 109/L) ITP for at least a year and an inadequate response to at least two prior treatments (median 6.5).
Participants received sutimlimab at a dose of 6.5 or 7.5 g depending on bodyweight (<75 or ≥75 kg, respectively) on days 0 and 7, after which the drug was administered every 2.0 weeks for a median of 14.6 weeks. Following a washout period of up to 9.0 weeks (median 2.1 weeks), six patients with evidence of treatment efficacy were retreated with sutimlimab every 2.0 weeks for a median of 71.6 weeks in the long-term extension phase of the study.
Broome noted that previously reported interim findings (data cutoff 14 December 2018) showed “a rapid, sustained increase in platelet count” following sutimlimab therapy in these patients, and added that the results remained promising in the current analysis, conducted at a cutoff of 9 April 2020.
Specifically, in the first part of the study, average platelet counts increased from 25 x 109/L at baseline to 54 x 109/L at 24 hours after initiation of sutimlimab and to 139 x 109/L at day 7, and remained greater than 50 x 109/L throughout part 1.
During washout, mean platelet counts dropped to 22 x 109/L, but rose to 65 x 109/L at day 4 and to 126 x 109/L at day 7 after retreatment with sutimlimab. This response was “sustained” through the duration of the extension phase, said Broome, and highlighted that the platelet responses in the initial and extension phases of the study “correlated very nicely” with changes in complement pathway activity.
| Response achieved | Response criteria (platelet count) | Proportion of patients (n=12) |
|---|---|---|
|
Overall response |
≥50 x109/L and ≥2-fold increase from baseline on 2 consecutive visits more than 7 days apart |
41.7% |
|
Complete response |
≥100 x109/L on 2 consecutive visits more than 7 days apart |
33.3% |
|
Durable response |
≥50 x109/L in ≥50% of visits from weeks 5 to 21 |
41.7% |
|
Time to response ≤2 days |
First time platelet count ≥50 x109/L |
33.3% |
In all, 41.7% of participants achieved an overall response, defined as a platelet count of at least 50 x 109/L and a greater than twofold increase from baseline at two consecutive assessments more than a week apart, and 33.3% had a complete response, defined as a platelet count of at least 100 x 109/L on two consecutive visits.
Additionally, 41.7% of patients had a platelet count of 50 x 109/L or higher in at least half of the assessments between weeks 5 and 21, without requiring rescue ITP therapy, and were therefore considered to have a durable response. And 33.3% responded to sutimlimab within 2 days of treatment initiation.
Reporting on the safety data, Broome said that half the patients in the initial and extension phases of the study had at least one treatment-emergent adverse event (TEAE) attributable to the study drug, but only one patient had at least one related serious TEAE and one had a serious infection.
Furthermore, there were no incidences of meningococcal infection or thromboembolic events, no patients discontinued the study due to a TEAE, and there were no deaths.
medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2021 Springer Healthcare Ltd, part of the Springer Nature Group
62nd ASH Annual Meeting and Exposition; 5–8 December 2020
Credits © royaltystockphoto/Fotolia
