What is the design of a TRIANGLE‑type trial using acalabrutinib for newly diagnosed mantle‑cell lymphoma patients aged 18‑65 years, stage II–IV, who are medically fit for autologous stem‑cell transplantation (ASCT)?

TRIANGLE Study Design Using Acalabrutinib

The TRIANGLE study design has not been directly replicated with acalabrutinib, but an analogous trial structure for transplant-eligible MCL patients aged 18-65 years would follow the established TRIANGLE framework with acalabrutinib substituted for ibrutinib.

Core Study Architecture

The TRIANGLE trial was a three-arm, randomized, open-label phase 3 superiority study that enrolled 870 patients with previously untreated stage II-IV mantle cell lymphoma, aged 18-65 years, who were medically fit for ASCT. 1 The study investigated whether adding ibrutinib to standard immunochemotherapy improved outcomes compared to standard treatment with ASCT, and whether ibrutinib-containing treatment without ASCT could replace the transplant approach. 1

Three Treatment Arms

The original TRIANGLE design consisted of: 1

• Arm A (Control): Six alternating cycles of R-CHOP and R-DHAP (or R-DHAOx) followed by ASCT
• Arm A+I (Experimental): Same chemotherapy backbone with ibrutinib 560 mg daily on days 1-19 of R-CHOP cycles, followed by ASCT, then 2 years of ibrutinib maintenance (560 mg daily)
• Arm I (Experimental): Ibrutinib with chemotherapy as in Arm A+I but ASCT omitted, with 2 years of ibrutinib maintenance

Acalabrutinib-Based TRIANGLE Adaptation

For an acalabrutinib-based TRIANGLE design, the dosing would be acalabrutinib 100 mg twice daily continuously during induction, consolidation, and maintenance phases, based on FDA-approved dosing and pharmacodynamic data showing ≥95% BTK occupancy maintained over 12 hours at this dose. 2

The three arms would be:

• Arm A: Standard R-CHOP/R-DHAP × 6 cycles → ASCT
• Arm A+Acala: R-CHOP/R-DHAP × 6 cycles with acalabrutinib 100 mg twice daily continuously → ASCT → acalabrutinib 100 mg twice daily maintenance for 2 years
• Arm Acala: R-CHOP/R-DHAP × 6 cycles with acalabrutinib 100 mg twice daily continuously (no ASCT) → acalabrutinib 100 mg twice daily maintenance for 2 years

Key Eligibility Criteria

Based on the TRIANGLE framework: 1

• Age 18-65 years
• Previously untreated MCL, stage II-IV
• Medically fit for ASCT
• Adequate organ function (specific thresholds would mirror TRIANGLE exclusions)

Primary and Secondary Endpoints

The primary endpoint would be failure-free survival, analyzed using three pairwise one-sided log-rank tests with statistical monitoring, following the TRIANGLE methodology. 1 Secondary endpoints would include overall response rate, complete response rate, overall survival, and safety assessments by treatment period. 1

Rationale for Acalabrutinib Substitution

Acalabrutinib demonstrates enhanced BTK selectivity with minimal off-target effects compared to ibrutinib, resulting in lower rates of atrial fibrillation and hypertension, which is particularly relevant given the substantial grade 3-5 hematological adverse events (50% of patients) and infections (25% of patients) observed with ibrutinib plus ASCT in the original TRIANGLE study. 1, 3 The ECHO trial demonstrated that acalabrutinib combined with bendamustine-rituximab achieved a median PFS of 66.4 months versus 49.6 months with placebo (HR 0.73, p=0.016) with manageable toxicity in older patients, supporting its efficacy in combination regimens. 2, 4

Critical Design Considerations

The TRIANGLE results showed that adding ibrutinib to standard treatment (Arm A+I) was superior to chemotherapy plus ASCT alone (Arm A) with 3-year failure-free survival of 88% versus 72% (HR 0.52, p=0.0008), but the comparison between Arm A and Arm I (ibrutinib without ASCT) did not demonstrate superiority of ASCT, suggesting that BTK inhibition may obviate the need for transplant consolidation. 1 This finding is particularly important for an acalabrutinib-based design, as it challenges the historical role of ASCT when potent BTK inhibition is incorporated. 5

A common pitfall would be using acalabrutinib only during induction cycles rather than continuously, as the pharmacodynamic data demonstrate that continuous dosing maintains sustained BTK occupancy and enzymatic inhibition throughout the treatment period. 2

Stratification Factors

Patients should be stratified by: 1

• Mantle Cell Lymphoma International Prognostic Index (MIPI) risk groups (low, intermediate, high)
• Study site/group

Risk stratification using pretreatment factors such as Ki67 proliferation index, MIPI-biologic score, and p53 status represents a high-priority design element for consolidation strategies, as recommended by consensus guidelines. 6