zilovertamab (UC-961)

P1, N=22, Completed, Barbara Parker, MD | Active, not recruiting --> Completed | Phase classification: P1b --> P1

The combination of zilovertamab and paclitaxel was safe and well tolerated in heavily pre-treated advanced breast cancer patients. Further evaluation of ROR1 targeting in breast cancer patients with zilovertamab is warranted.

P1, N=32, Recruiting, University of California, San Diego

P1/2, N=102, Active, not recruiting, Oncternal Therapeutics, Inc | Phase classification: P1b/2 --> P1/2

Co-culture of Jurkat-Lucia cells for 6 hours with the anti-CD20 mAb rituximab and MEC1 or MEC1-ROR1 cells induced Jurkat-Lucia cells to express a luciferase reporter gene under the control of an ISG54 minimal promoter fused to six NFAT response elements; this endowed the Jurkat-Lucia cells with high luminescence activity that was not observed in co-cultures of EC and TC without added mAb. ROR1 + CLL cells harboring del(17p) or mutations in TP53 (del(17p)/m TP53) and/or that were resistant to targeted therapies (e. g. , inhibitors of BTK or BCL2), were as susceptible to GE-zilovertamab-directed ADCC as were CLL cells without del(17p)/m TP53 from patients who had not had prior therapy. These data demonstrate that GE-zilovertamab can direct high-level ADCC lysis of ROR1-expressing neoplastic cells with greater activity than zilovertamab, encouraging development of clinical studies to evaluate GE-zilovertamab for therapy of patients with CLL or other ROR1-positive cancers.

P2, N=5, Active, not recruiting, University of California, San Diego | Recruiting --> Active, not recruiting | N=16 --> 5

P1, N=32, Recruiting, University of California, San Diego | Phase classification: P1b --> P1

In addition, a patient-derived xenograft (PDX) mouse model was also used for evaluating single agent and combination efficacy of BTKis and zilovertamab (Zilo)...Treatment with single BTKi at 2-10 µM (Ibrutinib, zanubrutinib, acalabrutinib or pirtobrutinib) significantly induced cytotoxicity in the TP53Mut MCL cells, and the cell death was remarkedly increased when BTKi was combined with Zilo at 25-50 µg/ml...Conclusion Dual targeting of BTK and ROR1 signaling pathways augmented efficacy selectively in preclinical MCL models with TP53Mut. These data provide insights to develop tailored therapeutics to improve patient outcome for patients with TP53 mutation.

Oncternal’s ONCT-808 autologous CAR T cells are genetically modified via ex vivo transduction with a self-inactivating lentivirus vector to express a ROR1-directed CAR containing single chain variable fragment derived from Oncternal’s clinical stage anti-ROR1 zilovertamab. In cancer therapy efficacy studies using CDX models, treatment with ONCT-808 cells resulted in complete tumor remission in ROR1 Jeko-1 cell-derived CDX mice, and controlled tumor growth in Raji cell-derived CDX mice, reflecting the specificity of the ONCT-808 cells to the ROR1 target. Conclusions ONCT-808 demonstrated high efficacy in inducing ROR1 specific cancer cell death in both in vivo and in vitro studies, suggesting its potential in treating human cancer patients.

Zilo + Ibr is well-tolerated with a safety profile that is comparable to Ibr alone. For pts with CLL, Zilo + Ibr is very active and results in durable remissions. The PFS and OS for the subgroup with TP53 mut/del(17p) are particularly encouraging in reference to other trials of BTK inhibitors, maintaining 100% PFS and OS at ∼42 mos.

We utilized the humanized scFv binding domain of zilovertamab (formerly UC-961 and then cirmtuzumab), which showed high affinity and specificity for human ROR1 and a highly favorable safety profile in Phase-1 clinical evaluation [1]...We conclude that lentivirus encoding this anti-ROR1 CAR construct can generate anti-ROR1 CAR T cells using T cells of healthy donors or patients with CLL that are highly effective in killing ROR1-expressing leukemia cells in vitro or in vivo. Moreover, the anti-ROR1 CAR T cells generated using this construct may provide for selective killing of CLL cells without affecting normal CD19/CD20-expressing B cells of patients with CLL, thereby mitigating the risk for further enhancing immune deficiency, such as observed in patients treated with anti-CD19 CAR T cell therapy.

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

P1b, N=22, Active, not recruiting, Barbara Parker, MD | Trial completion date: Jan 2023 --> Jan 2024

P1b/2, N=102, Active, not recruiting, Oncternal Therapeutics, Inc | Recruiting --> Active, not recruiting | Trial completion date: Apr 2027 --> Aug 2024 | Trial primary completion date: Mar 2025 --> Aug 2024

P3, N=365, Ongoing, Oncternal Therapeutics, Inc

Clinical studies using ROR1 targeting antibodies (Zilovertamab) to treat hematologic malignancies did not reveal relevant clinical toxicity, encouraging the initiation of clinical trials to assess the safety and efficacy of ROR1-CAR-T therapy... With this novel protocol, we aim to obtain the first manufacturing license for CAR-T in Europe that integrates our optimized approach with SB100X mRNA and MC for CAR gene-transfer on the MaxCyte transfection platform. The quality of the drug product supports the developement of a clinical trial with ROR1-CAR-T, and will serve as a blueprint for other CAR-T products.

This study demonstrates that an anti-ROR1 mAb, Zilovertamab, can eliminate up to 80% of AML LSC insupportive niches. In the future, targeted ROR1 inhibition may represent a vital component of therapeuticstrategies aimed at eradicating therapeutically recalcitrant LSCs in AML and potentially other refractorycancer stem cell-driven malignancies.

In this study, Zilo+Ibr is well-tolerated with a safety profile that is very similar compared with Ibr alone. With respect to grade ≥3 neutropenia in RR MCL, the rate observed with Zilo+Ibr was 9.1%, which is lower than the 29% reported for Ibr alone in its Phase 3 study. The combination is very promising in pts with RR MCL (ORR 85.2%, CR 40.7%, mPFS 35.9 mos), compared with historical results for Ibr alone (ORR 66%, CR 20%, mPFS 12.8 mos; Rule 2017).

The subsequent key areas hold promise: Alternative Inhibitors of BTK Here, non-covalent BTK inhibitors, such as pirtobrutinib (LOXO- 305) and nemtabrutinib (ARQ-531), have shown effi cacy in CLL resistant to covalent BTK inhibitors...AZD5991 is a highly selective BH3-mimetic that demonstrates high potency in MCL1-dependent cell lines.9 Our group has shown that selective targeting Mcl-1 induced metabolic dysfunction and abrogated survival of lymphoid cells in vitro and in vivo.10 Other BH3- mimetics targeting Mcl-1 include AMG-176 and S63845.11,12 However, Mcl-1 targeting agents may be associated with toxicities, including against the hematopoietic stem and progenitor cells, potentially leading to cytopenias in the clinic.13 The therapeutic window for these agents needs to be defi ned. BH3-mimetics which target Bcl-xL, such as navitoclax, are not being developed in CLL due to concerns of thrombocytopenia.14 However, AZD4320, an alternative Bcl-2/xL inhibitor, is being studied in lymphoid malignancies as an intravenous formulation, with hope to mitigate its effect on platelets.15 Therapeutic Antibodies Targeting surface receptors and inducing both direct and immunemediated apoptosis has been a success story in CLL with use of anti-CD20 agents...Lanalumab (VAY-736), a humanized defucosylated engineered antibody directed against BAFF-R, antagonized pro-survival effects of BAFF in CLL cells.16 In a phase 1 study in combination with ibrutinib in 32 patients with CLL, CR was achieved in 38% of patients, and 42% demonstrated undetectable minimal residual disease (uMRD) in the blood/bone marrow, a promising result not expected with ibrutinib alone.17 Alternative targets for therapeutic antibodies include ROR1 (cirmtuzumab) and CD19 (tafasitamab)...A recent report of a phase 1/2 study of lisocabtagene maraleucel, an autologous CD19-directed CAR T-cell therapy (TRANSCEND CLL 004), confi rmed effi cacy in patients with relapsed/refractory CLL.18 In this study, patients had a median of 4 prior therapies, including ibrutinib and venetoclax...In a Phase 1/2 trial, HLA-mismatched CD19-targeting CAR NK cells induced CRs in patients with CLL after a single infusion and without CRS or neurotoxicity attributable to the cellular product.19 Finally, bi-specifi c antibodies have demonstrated impressive effi cacy in non-Hodgkin lymphoma and are also an off-the-shelf product which boasts high tolerability. Development of bi-specifi c antibodies in CLL is still in early stages, however epcoritamab (a subcutaneously administered CD3xCD20 Duobody) demonstrated responses in an ongoing Phase 1 study.20 In sum, targeted therapy replaced chemo-immunotherapy in treatment of CLL, and emerging small molecule and cell therapy approaches auger an expansion of the therapeutic armamentarium for CLL in the next decade.

P1b, N=32, Recruiting, University of California, San Diego | Not yet recruiting --> Recruiting | Phase classification: P2 --> P1b

Our ROR1 CAR-T cells controlled the solid tumor growth without causing any severe toxicity. Our results demonstrated that ROR1 CAR-T derived from Zilovertamab is efficacious and safe to suppress ROR1 solid tumors in vitro and in vivo, providing a promising therapeutic option for future clinical application.

P1b/2, N=138, Recruiting, Oncternal Therapeutics, Inc | Active, not recruiting --> Recruiting | Trial primary completion date: Jun 2025 --> Mar 2025

Treatment of primary CLL cells with Wnt5a also increased their resistance to venetoclax, an effect that could be inhibited by the anti-ROR1 mAb (UC-961, zilovertamab). Collectively, these studies indicate that Wnt5a-induced ROR1-signaling can enhance resistance to venetoclax therapy.

P1b, N=22, Active, not recruiting, Barbara Parker, MD | Trial completion date: Jan 2022 --> Jan 2023

Study ZILO-302 data may also support additional labeling for the combination of ZILO plus Ibr. Conclusion Study ZILO-301, a phase 3, multinational, double-blind, placebo-controlled study is open for enrollment in June 2022.

Conclusion The zilovertamab-based CAR tested in this study enhances the NK cell response towards ROR1-expressing cancer cells and enables T cells to clear fast-growing cancer cells in an in vivo model. These findings support the development of anti-ROR1 cell therapies for the potential treatment of ROR1-positive hematological malignancies.

The aim of this study was to investigate the potential of zilovertamab alone, or in combination with commonly utilised gynaecological cancer therapies (cisplatin, paclitaxel and the PARP inhibitor-Olaparib) on high-grade serous ovarian cancer (HGSOC), including models of platinum resistance and homologous recombination deficiency (CaOV3, CaOV3CisR, PEO1 and PEO4) and endometrial cancer (EC) cell lines (Ishikawa and KLE). In general, the addition of commonly used chemotherapies to a fixed dose of zilovertamab did not enhance the observed anti-proliferative activity. This study supports the potential of zilovertamab, or other ROR1-targeting therapies, for treating women with HGSOC and EC.

P1b/2, N=160, Active, not recruiting, Oncternal Therapeutics, Inc | Recruiting --> Active, not recruiting

ROR1 was expressed at high levels on castration resistant small cell PCa and neuroendocrine PCa models in PCa cell lines and PDX models. Cirmtuzumab has demonstrated efficacy in our patient derived xenograft organoid cultures. These studies have formed the rationale for development of a Phase 1b clinical trial of Cirmtuzumab in combination with docetaxel in metastatic CRPC patients.

HMCLs with high endogenous ROR1 expression were sensitive to in vitro killing by anti-ROR1 CAR T-cell treatment, which employs an scFv generated from the fully humanized ROR1-specific monoclonal antibody cirmtuzumab, at effector:target cell ratios (ET) as low as 0.33:1. Together, these results suggest a central role for Wnt signaling in MM stem cell phenotypes and activation of embryonic transcriptional pathways, while also paving the way towards development of clinical therapies that target a CSC population in MM.

Cirm/Ibr is well-tolerated. ORR, CR, DOR, and mPFS were similar across all subgroups of MCL and CLL pts regardless of number of prior systemic regimens or poor risk factors. Striking responses were observed in patients with MCL as evidenced by a mPFS that was NR (95% CI: 16.5, NR), CR of 35%, and a DOR of NR (95% CI: 11.9, NR) within the study period.

AZD5991 is a highly selective BH3-mimetic that demonstrates high in vitro potency in MCL1-dependent cell lines with an IC50 <1 nM.7 We have demonstrated that direct MCL1 inhibition with AZD5991 disrupts survival of neoplastic B-cells in lymph-node mimicking conditions, induces mitochondrial dysfunction and cooperates with BCL2/X inhibitors in vitro and in vivo.8 A phase 1 clinical trial of AZD5991 alone or in combination with venetoclax in hematologic malignancies is ongoing (NCT03218683)...AMG-176 demonstrated synergy with venetoclax in AML models; however, it also caused cytopenias.9 AMG-176 was shown to induce apoptosis of CLL cells independent of prognostic markers and overcame the protective effect of stromal microenvironment.10 However, suppressive effects on hematopoiesis will likely become the dose- limiting factor in clinical trials of MCL1-targeting agents. The effect of MCL1 inhibition on cord blood-derived CD34+ cells was studied using a small-molecule inhibitor, S63845,11 resulting in almost complete depletion of human hematopoietic stem and progenitor cells, while mature blood cells survived normally...We have shown that SYK inhibition with entospletinib leads to downmodulation of MCL1 protein in CLL both in vitro and in the clinic.12,13 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.13 Entospletinib has shown promising clinical activity in CLL.12,14 It is currently being developed in myeloid malignancies.15 A novel dual SYK/BTK inhibitor luxeptinib also was shown to downregulate MCL1 and other pro-survival BCL2 proteins in CLL.16 Transcriptional cyclin-dependent kinases (CDK7/9) regulate activity of RNA polymerase, thereby controlling production of mRNA. Downmodulation of MCL1 has been considered a key mechanistic event accounting for the pro-apoptotic activity of CDK inhibitors in neoplastic B-cells.17,18 Pan-CDK inhibitors (flavopiridol, dinaciclib) demonstrate clinical efficacy in lymphoid malignancies. We and others reported that preclinical efficacy of AZ5576, a selective inhibitor of CDK9, and its clinical congener AZD4573 in lymphoid tumors depended on rapid downmodulation of MCL1, BFL1, and MYC.19–21 CDK9 inhibition can increase efficacy of BH3-mimetics, but safety of this combination will need to be explored.22,23 CDK9 inhibitors in development, in addition to AZD4573, include VIP152, CYC065, and voruciclib...Navitoclax is a small-molecule inhibitor of BCL2, BCLX, and BCL2L2; however, its use in CLL has been plagued by thrombocytopenia.24 AZD4320 is an alternative agent that co-targets BCL2/X...ABBV-155, an antibody-drug conjugate targeting BCLX, where BCLX is being used as a payload to avoid “off-tumor” effects, demonstrated promise in solid tumor models.26 Finally, as many microenvironment-driven pro-survival pathways converge on NFB, leading to induction of chemokines, cell cycle regulators, and BCL2 family proteins themselves, this transcription factor continues to be an attractive target in CLL...When combined with ibrutinib in murine CLL models, VAY-736 produced prolonged survival compared with either therapy alone.28 Alternative targets for therapeutic antibodies include ROR1 (cirmtuzumab), CD19 (tafasitamab), and others.29 As resistance to novel agents is becoming an unmet need in CLL, exploration of novel targets is of paramount importance...Multiple CDK inhibitors are currently being explored and have anti-tumor effects not restricted to MCL1 inhibition. CAR T cells and bi-specific antibodies have exceptional efficacy in lymphoid malignancies and thus are of high relevance in CLL.

P1b/2, N=160, Recruiting, University of California, San Diego | Trial completion date: Dec 2022 --> Jun 2027 | Trial primary completion date: Oct 2020 --> Jun 2025

P1b, N=22, Active, not recruiting, Barbara Parker, MD | Recruiting --> Active, not recruiting | N=15 --> 22 | Trial completion date: Jun 2021 --> Jan 2022

Viability of ROR1-high primary CLL cells cultured in serum-free media, with or without cirmtuzumab (20 μg/mL) with or without exogenous Wnt5a (200 ng/mL) and with venetoclax at concentrations ranging from 0.5nM to 4nM, was determined at 16h. Conclusion Collectively, these studies indicate that expression of ROR1 can enhance cancer-stemness and venetoclax resistance. Because the resistance of CLL cells to venetoclax can be enhanced by WNT5a-induced ROR1 signaling, strategies targeting ROR1 may enhance the efficacy of venetoclax-based regimens and/or mitigate the risk of developing PD on venetoclax therapy.

P1b, N=15, Recruiting, Barbara Parker, MD | N=30 --> 15

The aim of this study was to investigate any anti-proliferative effect of cirmtuzumab in combination with commonly-used gynaecological cancer therapies (cisplatin, paclitaxel and the PARP inhibitor, olaparib) on high grade serous ovarian cancer (HGSOC) and EC cell lines including models of platinum resistance. Cirmtuzumab alone inhibited proliferation of ovarian cancer and EC cells in vitro, and could enhance the activity of commonly-used chemotherapeutic agents. This study supports the potential of cirmtuzumab or other ROR1 targeting therapies for treating women with HGSOC and EC.

Collectively these studies demonstrate that Wnt5a-induced ROR1-signaling in CLL promotes cancer dedifferentiation/stemness and increases resistance to Ven. Strategies that inhibit ROR1-signaling with agents such as cirmtuzumab may enhance the cytotoxic activity of venetoclax and/or mitigate risk of developing resistance to venetoclax therapy.