VALENTINE-PTCL01

Background

Phase II, single-arm, multicenter, international study. 119 efficacy-evaluable patients with relapsed/refractory PTCL after ≥1 prior therapy. Valemetostat is an oral dual EZH1/EZH2 inhibitor; dual inhibition overcomes EZH1 compensation seen with EZH2-only blockade. AITL epigenetic dysregulation (IDH2, TET2, DNMT3A mutations) supports this approach.

Interventions and follow up

Regimen: Valemetostat 200 mg PO once daily continuously in R/R PTCL (dual EZH1/2 inhibitor)
Primary endpoint: Overall response rate (independent review committee)
Median follow-up: 12.3 months

Results

ORR (primary): 44% (95% CI 35–53%)
CR rate: 22%
AITL subgroup ORR: 52%
Median DoR: 6.6 months
Median PFS: 4.9 months

Adverse events

Hematologic: Grade 3–4 thrombocytopenia 23%; grade 3–4 anemia 19%; grade 3–4 neutropenia 17%
Dermatologic/constitutional: Alopecia any grade 46%; nausea any grade 40%; dysgeusia 26% (grade 3–4 0%)
Overall: Discontinuation for AEs 13%

Conclusions

Valemetostat achieved a 44% ORR with activity across PTCL subtypes including AITL (52% ORR), establishing dual EZH1/2 inhibition as a clinically active strategy in R/R PTCL with a convenient oral, once-daily schedule.

Key Limitations

Single-arm Phase II with no randomized comparator and relatively short median DoR (6.6 months) and PFS (4.9 months). Alopecia (46%) is a notable cosmetic toxicity. Longer follow-up is needed to assess response durability.

Clinical Context

Valemetostat is approved in Japan for R/R PTCL and ATLL; it is not yet FDA or EMA approved for PTCL (US accelerated approval applies to R/R ATLL). VALENTINE-PTCL01 supports dual EZH1/2 inhibition as an emerging oral option for R/R PTCL, with epigenetic targeting especially relevant in TFH-phenotype/AITL disease per ESMO discussion of novel agents.

References