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Myelofibrosis (MF) is a myeloproliferative neoplasm characterized by splenomegaly and significant symptom burden.1 Although the Janus kinase inhibitor ruxolitinib has improved splenomegaly and MF-related symptoms in patients with MF, the majority achieve suboptimal responses.1
Navtemadlin is a potent, selective, oral, mouse double minute 2 inhibitor (MDM2i) that restores p53 activity and modulates the expression of pro-apoptotic Bcl-2 family proteins to induce apoptosis of TP53wt CD34+ myeloblasts.1 In a phase II study, single-agent navtemadlin demonstrated promising clinical and disease-modifying activity in patients with relapsed/refractory MF. Preclinical studies have demonstrated the synergistic effects of navtemadlin plus ruxolitinib in mediating p53-dependent apoptosis of myeloblasts by inhibiting checkpoint p21-mediated cell-cycle arrest, providing the rationale for investigation of the combination in the clinical setting.1
Below, we summarize one of our European Hematology Association (EHA) 2023 top abstracts reporting the efficacy and safety of navtemadlin combined with ruxolitinib in patients with primary or secondary MF who have a suboptimal response to ruxolitinib, presented by John Mascarenhas.1
KRT-232-109 (NCT04485260), is a global, open-label, multicenter, phase IIb/II study, which included patients with:
The phase I dose escalation evaluated three doses of navtemadlin (120 mg, 180 mg, and 240 mg) added to a pre-study ruxolitinib dose (≥8 weeks) to identify the recommended phase II expansion dose (RP2D). In the phase II dose expansion, navtemadlin at 240 mg was administered for 7 days, with 21 days off in a 28-day cycle.
Primary endpoints:
Key secondary endpoints:
Overall, 28 patients were treated with navtemadlin at the RP2D of 240 mg. Baseline characteristics are summarized in Table 1.
Table 1. Baseline characteristics*
DIPPS, Dynamic International Prognostic Scoring System; MF, myelofibrosis; TSS, total symptom score. |
|
Characteristic, % (unless otherwise stated) |
Navtemadlin 240 mg + ruxolitinib |
---|---|
Median age at diagnosis (range), years |
63 (40–85) |
DIPPS |
27 |
Intermediate 1 |
43 |
Intermediate 2 |
32 |
High |
25 |
MF subtype |
|
Primary |
36 |
Secondary |
64 |
Median spleen volume at baseline (range), cm3 |
2,039 (650–3,549) |
Median platelets (range), 106/L |
165 (100–636) |
Transfusion dependence, n |
25 |
Median prior lines of therapy (range), n |
1 (1–5) |
Median TSS (range) |
15 (3.2–49.1) |
Median duration of prior ruxolitinib therapy (range), months |
21.6 (7–129) |
Ruxolitinib dose at entry† |
|
5 mg |
14 |
10 mg |
25 |
15 mg |
18 |
20–25 mg |
39 |
Among evaluable patients (n = 19) at the May 2, 2023, data cut off:
Among seven evaluable patients, 71% achieved a ≥20% reduction of driver VAF, and 57% had improved bone marrow fibrosis of Grade >1 by central review.
Overall, treatment emergent adverse events (TEAEs) were mostly Grade 1–2. Any grade and Grade 3–4 TEAEs were reported in 96% and 46% of patients, respectively.
Figure 1. Any grade TEAEs in ≥10%*
*Data from Mascarenhas.1
This phase II study demonstrated the clinically meaningful benefit and safety of navtemadlin plus ruxolitinib in patients with primary or secondary MF who had a suboptimal response to ruxolitinib. This combination resulted in reduced spleen volume, reduced symptom burden, reduced percentage of CD34+ cells, as well as driver VAF and bone marrow fibrosis reductions, with low incidences of high-grade adverse events. These data support the evaluation of this novel combination in a phase III study.
References
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