Question 1

What is sonrotoclax and what does the CELESTIAL-RRMCL Phase 3 trial test?

Accepted Answer

Sonrotoclax (BGB-11417) is BeOne Medicines's BCL-2 inhibitor, designed as an improved successor to venetoclax with potentially greater selectivity for BCL-2 over BCL-XL. BCL-2 (B-cell lymphoma 2) is an anti-apoptotic protein highly expressed in mantle cell lymphoma that allows tumor cells to evade programmed cell death. Venetoclax (Venclexta) is approved in CLL/AML and has shown activity in MCL in relapsed/refractory settings, but MCL-specific approval is limited. The CELESTIAL-RRMCL Phase 3 trial (NCT06742996) tests sonrotoclax in combination with zanubrutinib (BeOne's BTK inhibitor, approved in MCL as Brukinsa) versus placebo plus zanubrutinib in adults with relapsed/refractory MCL. The hypothesis is that adding a BCL-2 inhibitor to a next-generation BTK inhibitor creates synergistic apoptotic pressure on MCL cells — a strategy supported by preclinical rationale showing BTKi + BCL-2i co-dependency in B-cell lymphoma models. If positive, CELESTIAL-RRMCL would establish a new standard of care in R/R MCL and create a direct comparison to venetoclax + BTKi combinations being explored in academic settings.

Question 2

What is pirtobrutinib (Jaypirca) and how does it work in BTK-inhibitor-resistant MCL?

Accepted Answer

Pirtobrutinib (Jaypirca, Eli Lilly) is a non-covalent BTK inhibitor — it binds BTK reversibly rather than forming the covalent bond at C481 that ibrutinib, acalabrutinib, and zanubrutinib require. This is clinically important because the most common mechanism of resistance to covalent BTKis (ibrutinib, acalabrutinib, zanubrutinib) is the C481S mutation in BTK, which prevents covalent bond formation and eliminates drug binding. Pirtobrutinib binds BTK independently of C481S status, restoring kinase inhibition in cells that have evolved covalent BTKi resistance. The FDA approved pirtobrutinib in 2023 for relapsed/refractory MCL after two prior lines including a covalent BTKi. MD Anderson is running two Phase 2 trials: NCT05529069 tests pirtobrutinib with venetoclax in R/R MCL (adding BCL-2 inhibition to non-covalent BTKi); NCT06263491 tests pirtobrutinib with rituximab in previously untreated low/intermediate-risk MCL (exploring whether non-covalent BTKi can replace chemoimmunotherapy in frontline MCL).

Question 3

What is a BTK protein degrader and how do BGB-16673 and NX-2127 differ from BTK inhibitors?

Accepted Answer

BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib, pirtobrutinib) block BTK kinase activity but leave the BTK protein intact — allowing resistance through protein overexpression, kinase-domain bypass mutations, or non-kinase BTK scaffolding functions. BTK degraders use a PROTAC (proteolysis-targeting chimera) or molecular glue approach: they recruit an E3 ubiquitin ligase to the BTK protein, marking it for proteasomal degradation and eliminating the entire protein rather than just its activity. BGB-16673 (BeOne Medicines, NCT05006716) is a BTK CDAC (chimeric degrader) that recruits the CRBN/CRL4 E3 ligase complex to degrade BTK. NX-2127 (Nurix Therapeutics, NCT04830137) is a BTK/IKZF1/3 degrader — it simultaneously degrades BTK and the IKZF1/IKZF3 transcription factors (Ikaros/Aiolos), potentially adding an IMiD-like immunomodulatory mechanism to BTK elimination. Both are in Phase 1 in relapsed/refractory B-cell malignancies including MCL. The key hypothesis: degraders could overcome C481S and non-C481S BTKi resistance by eliminating the BTK protein entirely, regardless of mutation status.

Question 4

What role does CAR-T cell therapy play in MCL, and why is glofitamab being tested after CAR-T failure?

Accepted Answer

KTE-X19 (brexucabtagene autoleucel, Tecartus) is the only approved CAR-T in MCL — approved in 2020 for relapsed/refractory MCL after two prior lines, with an overall response rate of ~87% and complete response of ~62% in the ZUMA-2 trial. However, approximately half of patients who achieve response will relapse, and the post-CAR-T setting in MCL is an emerging area with no established standard of care. Glofitamab (Columvi, Roche/Genentech) is a bispecific CD20xCD3 T-cell engager approved in R/R DLBCL. The NCI Phase 2 trial (NCT07003295) tests glofitamab specifically in MCL patients whose disease returned after CAR-T — testing whether a bispecific T-cell engager, which recruits endogenous T cells rather than infused CAR-T cells, can induce remission in the post-CAR-T setting where T-cell exhaustion and tumor immune evasion are primary failure mechanisms.

Question 5

What is the current standard of care for mantle cell lymphoma in 2026?

Accepted Answer

MCL treatment in 2026 is broadly stratified by patient fitness and line of therapy. For transplant-eligible patients in first-line treatment, intensive chemoimmunotherapy (R-DHAP, R-CHOP alternating, cytarabine-based induction) followed by autologous stem cell transplantation (ASCT) remains a standard for young fit patients — though this paradigm is being challenged by frontline BTKi-containing regimens (ibrutinib + BR, acalabrutinib combinations). For transplant-ineligible patients, R-CHOP or bendamustine + rituximab (BR) is typically used. In relapsed/refractory MCL: (1) First R/R: covalent BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib) are the backbone; (2) Post-covalent BTKi: pirtobrutinib (approved) or KTE-X19 CAR-T (approved after 2+ prior lines including BTKi); (3) Post-CAR-T: no standard — glofitamab, BTK degraders, and venetoclax combinations are under investigation. Zanubrutinib is increasingly preferred over ibrutinib based on superior safety data (ALPINE trial in CLL; MCL approval also in place).

NCT ID	Drug / Mechanism	Sponsor	Status
NCT05529069	Pirtobrutinib + venetoclax — non-covalent BTKi + BCL-2i in R/R MCL	MD Anderson Cancer Center	Recruiting
NCT06263491	Pirtobrutinib + rituximab — non-covalent BTKi in previously untreated low/intermediate-risk MCL	MD Anderson Cancer Center	Recruiting
NCT07003295	Glofitamab — CD20xCD3 bispecific T-cell engager in MCL after CAR-T failure	NCI	Recruiting

NCT ID	Drug / Mechanism	Sponsor	Status
NCT05006716	BGB-16673 — BTK CDAC protein degrader in R/R B-cell malignancies including MCL	BeOne Medicines	Recruiting
NCT04830137	NX-2127 — BTK/IKZF1/IKZF3 degrader in R/R B-cell malignancies including MCL	Nurix Therapeutics	Recruiting
NCT06026319	CD79b-19 CAR T cells — dual-antigen CAR-T in Non-Hodgkin Lymphoma including MCL	Mass General / MGH Cancer Center	Recruiting

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