NX-2127

Treatment of chronic lymphocytic leukemia with NX-2127 achieves >80% degradation of BTK in patients and demonstrates proof-of-concept therapeutic benefit. These data reveal an oncogenic scaffold function of mutant BTK that confers resistance across clinically approved BTK inhibitors but is overcome by BTK degradation in patients.

NX-2127 is orally bioavailable, exhibits in vivo degradation across species, and demonstrates efficacy in preclinical oncology models. NX-2127 has advanced into first-in-human clinical trials and achieves deep and sustained degradation of BTK following daily oral dosing at 100 mg.

P1, N=160, Active, not recruiting, Nurix Therapeutics, Inc. | Recruiting --> Active, not recruiting

This first-in-human study of NX-2127 is actively enrolling and dose-expansion cohorts in DLBCL and MCL have been initiated at the 300 mg daily dose. Findings include dose-dependent PK accompanied by degradation of BTK and Ikaros. Encouraging and persistent responses were observed in heavily pretreated patients with relapsed/refractory CLL and NHL with a manageable safety profile.

P1, N=160, Recruiting, Nurix Therapeutics, Inc. | Trial completion date: Nov 2023 --> Dec 2025 | Trial primary completion date: Oct 2023 --> Dec 2024

In addition to direct anti-neoplastic effects, BTK inhibitors ibrutinib and acalabrutinib were found to favorably modulate T-cell function in pre-clinical and clinical studies of CLL...In vitro polarization assays indicated that treatment with 1 μM NX-2127, but not NX-5948, resulted in a dramatic and significant upregulation of both IFN-γ and IL-2 under TH1-polarizing conditions, to a degree which significantly exceeded the effect of either ibrutinib or lenalidomide... CRBN-recruiting BTK degraders NX-2127 andNX-5948 induce degradation of BTK in primary CLL cells and do not interfere with T-cell activation and survival in vitro. More importantly, CRBN-immunomodulatory activity was required to upregulate CD38 (an IFN response gene), promote T-cell differentiation towards a TH1 phenotype, downregulate Treg differentiation, and facilitate immunological synapse formation, suggesting NX-2127 has the potential to reverse the immunosuppressive environment of CLL. Overall, our findings provide a strong rationale for continued investigation of these BTK degraders in CLL and lymphoid malignancies.

The C481S and C481R mutations eliminated the anti-proliferative effects of covalent inhibitors ibrutinib, acalabrutinib, and zanubrutinib, whereas the V416L, T474I, and L528W mutations had variable effects on the covalent inhibitors. By contrast, the non-covalent inhibitors pirtobrutinib, vecabrutinib, and fenebruitnib maintained activity against C481S but displayed partially reduced potency against the C481R mutation and dramatically reduced potency against the V416L, T474I, and L528W mutations...These degrader molecules may also have utility in earlier lines of therapy due to their ability to suppress scaffold-mediated BTK signaling. Phase 1a/b trials of NX-5948 and NX-2127 in patients with relapsed or refractory B-cell malignancies are ongoing (NX-5948: NCT05131022; NX-2127: NCT04830137).

1, 2 Treatment of CLL cells with entospletinib, but not other BCR-signaling inhibitors, led to a disruption of BAFF-BCR cross-talk and downmodulation of MCL1 mRNA and protein, thus implicating SYK in transduction of multiple pro-survival signals emanating from the tumor microenvironment.1 Entospletinib has shown promising clinical activity in CLL, alone or in combination with obinutuzumab, including in patients with high-risk disease such as TP53 aberrant.3, 4 The drug is very well tolerated, however its development in CLL has been halted. Meanwhile, we have shown that luxeptinib, a dual SYK/BTK kinase inhibitor, has activity in BTK inhibitor-resistant lymphoid models in vitro.5 Luxeptinib is now being investigated in lcinical trials in hematologic malignancies...The early results of MS-553, a selective PKC-β inhibitor, indicates that this agent is tolerable and effective both as single agent and in combination with venetoclax.8 Proteolysis-targeting chimeras (PROTACs) are a new class of small molecules with two covalently-linked ligands recruiting target protein and E3 ubiquitin ligase together to trigger and enable proteasomal degradation of the target protein.9 “BTK degraders”, such as NRX- 2127 (Nurix Therapeutics) and BGB-16673 (Beigene), have entered clinical trials in patients with lymphoid malignancies...Additionally, NX-2127 has shown preclinical activity similar to immunomodulatory drugs (IMiDs) by catalyzing the ubiquitination of Ikaros (IKZF1) and Aiolos (IKZF3), resulting in increased T-cell activation.10 Early results of an ongoing clinical trial of NX-2127 demonstrate an ORR of 33% in heavily pre-treated patients with CLL, and overall good tolerability 11...The preclinical activity of AZD5991 has shown that selective targeting of MCL1 induced metabolic dysfunction and abrogated survival of diffuse large B cell lymphoma and ibrutinib-resistant mantle cell lymphoma cell lines in vivo and in vitro.13 Other BH3-mimetics targeting MCL1 include AMG176 and S63845.14-16 In an experimental design testing the effects of AMG-176 on CLL and normal hematopoietic cell death it was demonstrated that AMG-176 is an active agent in inducing CLL cell death while sparing normal blood cells...Anti-CD20 monoclonal antibodies – rituximab, obinutuzumab and ofatumumab – have significantly improved the survival outcomes. The B cell activating factor receptor (BAFF-R) is one of the main pro-survival receptors in B cells.18 In a preclinical study, ianalumab (VAY-736), a humanized defucosylated engineered antibody directed against BAFF-R, antagonized pro-survival effects of BAFF in CLL cells and showed promising activity both as a single agent and in combination with ibrutinib.19 A phase 1 study of dose escalation and dose expansion investigated the combination of ianalumab with ibrutinib in 32 patients with CLL with median one prior line of therapy (range, 0-4)...This study showed promising results not expected with ibrutinib alone.20 Tafasitamab – a Fc-enhanced, humanized, monoclonal antibody to CD19 – in combination with idelalisib or venetoclax in 24 patients has been associated with an ORR of 77% and 91%, respectively...In a phase 1 study involving 26 patients with R/R CLL, cirmtuzumab administered at four biweekly infusions was shown to have a long plasma half-life and did not have dose-limiting toxicity, potentially providing another treatment opportunity for patients with CLL.22 Immune Cell Enabling Therapies...A recent report of a phase 1/2 study of lisocabtagene maraleucel, an autologous CD19-directed CAR T-cell therapy (TRANSCEND CLL 004), confirmed efficacy in patients with R/R CLL.23 In this study, 23 patients with median 4 prior lines of therapy (range 2-11) were enrolled, 10 of whom were considered double exposed/refractory...In total, 65% of patients required administration of tocilizumab and/or corticosteroids.23 In addition to the ongoing phase 2 portion of this study, efforts now focus on innovative CAR T-cell designs as well as combination strategies...A phase 1b/2 ongoing trial is currently examining the safety and tolerability of the product in patients with R/R CLL. The early results suggest that epcoritamab administered subcutaneously is well tolerated in a heavily pretreated patient population with multiple high-risk features and shows clinical activity.25 Furthermore, an ongoing study is demonstrating preliminary efficacy of epcoritamab in patients with Richters transformation, a notoriously difficult-to-treat complication of CLL.26

Observations regarding the importance of B-cell receptor signalling for the survival and proliferation of CLL cells led to the development of the first-in-class BTK inhibitor (BTKi), ibrutinib, for the treatment of CLL...As a result, more specific inhibitors of BTK were developed, such as acalabrutinib and zanubrutinib, which have demonstrated equivalent/enhanced efficacy and improved tolerability in large randomized clinical trials...As these drugs all bind covalently to BTK, an alternative approach was to develop noncovalent inhibitors of BTK, including pirtobrutinib and nemtabrutinib...A further step in the clinical development of BTK inhibition has been the introduction of BTK degraders, which remove BTK by ubiquitination and proteasomal degradation, in marked contrast to BTK inhibition. This article will review the evolution of BTK inhibition for CLL and offer future perspectives on the sequencing of an increasing number of different agents, and how this may be impacted on by mutations in BTK itself and other kinases.

Combination therapy with ibrutinib, lenalidomide and rituximab demonstrated clinical activity in recurrent DLBCL [Goy et al. In this first-in-human, first-in-class study of a BTK degrader, NX-2127 was well tolerated and showed promising activity in a patient with non-GCB DLBCL. These data support further clinical development of NX-2127 in B cell lymphoid malignancies including DLBCL.

In pre-clinical safety studies, NX-2127 demonstrates an acceptable safety profile. NX-2127 is currently in phase 1 clinical trials (NCT04830137) for hematological malignancies.

Preclinical data support the activity of NX-2127 in tumor models harboring either wild-type BTK or BTK-mutants conferring clinical resistance to approved and investigational inhibitors. NX-2127 is currently being evaluated in an ongoing Phase 1 trial for patients with relapsed or refractory B-cell malignancies (ClinicalTrials.gov NCT04830137).

All have previously received a BTKi and 76.5% had also received venetoclax. Double- and emerging triple-refractory CLL (patients who progressed on cBTKi, ncBTKi, and a BCL2 inhibitor) represents a major unmet medical need with no approved therapeutic options and poor survival. These patients may thus benefit from the interruption of BTK kinase-independent scaffolding signaling. In this first-in-human, first-in-class study of a BTK degrader, clinical responses and benefit were observed in heavily pretreated (median 6 prior therapies) patients with CLL who have poor prognostic factors, including those with BTK mutations resistant to cBTKi and ncBTKi, BCL2 mutations and those who were previously treated with both BTKi and BCL2 inhibitors.

Covalent BTK inhibitors (BTKis), including ibrutinib and acalabrutinib, irreversibly bind to cysteine 481 in the kinase domain of BTK, inhibit growth, and induce loss of viability of MCL cells...In the present studies, we determined that in vitro exposure of human MCL cells, including MCL cell lines: REC1, Mino and JeKo-1, as well as patient-derived (PD) MCL cells, to NX-2127 (10 to 250 nM) for 2 to 24 hours markedly depleted BTK levels via proteasomal degradation, since co-treatment with the proteasome inhibitor carfilzomib restored BTK levels. NX-2127 but not NX-5948 treatment also degraded and depleted IKZF1 and IKZF3 levels...Co-treatment with NX-2127 (10 to 100 nM) and low nM levels of venetoclax or ABBV-744 was synergistically lethal against MCL cells (Delta synergy score above 1.0 by ZIP method). Collectively, these findings demonstrate that treatment with NX-2127 degrades and attenuates BTK and IKZF1/3 levels, as well as inhibits the downstream pro-growth and pro-survival signaling, resulting in loss of viability of MCL cells, including those resistant to covalent BTKi treatment. These findings also show promising anti-MCL activity of NX-2127-based combination with BCL2 or BET inhibitor which merits further in vivo validation.

Immunomodulatory drugs (IMiDs, e.g., lenalidomide) are approved as monotherapy for follicular lymphoma (FL), MZL, and MCL, in combination with other therapies for diffuse large B-cell lymphoma (DLBCL) and have shown synergy with BTK-targeted therapy...NX-2127 was shown to degrade both wild-type (WT) and C481-mutated (ibrutinib-resistant) BTK protein in vitro...The primary endpoint are dose-limiting toxicities and maximum tolerated dose (Phase 1a), objective response (Phase 1b), and safety (Phase 1a and Phase 1b) of NX-1607...Conclusion Accrual is ongoing. Clinical trial information: NCT04830137.

P1, N=130, Recruiting, Nurix Therapeutics, Inc.