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•CD33/CD123 NANOBODY TCE kills single and double-positive cells, outperforming single-targeting TCE in a subset of AML samples.•CD33/CD123-TCE efficiently kills AML cells in a mouse model and targets cells in nonhuman primates without signs of cytokine release.

Anti-CD38 monoclonal antibodies (mAbs) represent a breakthrough in the treatment of multiple myeloma (MM), yet some patients fail to respond or progress quickly with this therapy, highlighting the need for novel approaches. In this study we compared the preclinical efficacy of SAR442085, a next-generation anti-CD38 mAb with enhanced affinity for activating Fcγ receptors (FcγR), with first-generation anti-CD38 mAb daratumumab and isatuximab. In surface plasmon resonance and cellular binding assays, we found that SAR442085 had higher binding affinity than daratumumab and isatuximab for FcγRIIa (CD32a) and FcγRIIIa (CD16a). SAR442085 also exhibited better in vitro antibody-dependent cellular cytotoxicity (ADCC) against a panel of MM cells expressing variable CD38 receptor densities including MM patients’ primary plasma cells. The enhanced ADCC of SAR442085 was confirmed using NK-92 cells bearing low and high affinity FcγRIIIa (CD16a)-158F/V variants. Using MM patients’ primary bone marrow cells, we confirmed that SAR442085 had an increased ability to engage FcγRIIIa, resulting in higher natural killer (NK) cell activation and degranulation against primary plasma cells than preexisting Fc wild-type anti-CD38 mAbs. Finally, using huFcgR transgenic mice that express human Fcγ receptors under the control of their human regulatory elements, we demonstrated that SAR442085 had higher NK cell-dependent in vivo antitumor efficacy and better survival than daratumumab and isatuximab against EL4 thymoma or VK*MYC myeloma cells overexpressing human CD38. These results highlight the preclinical efficacy of SAR442085 and support the current evaluation of this next-generation anti-CD38 antibody in phase I clinical development in patients with relapsed/refractory MM.

Background:

Acute myeloid leukemia (AML) is the most common adult hematologic malignancy. Relapse is common and salvage treatment with cytotoxic chemotherapy is rarely curative. Immunotherapy targeting surface antigens expressed in leukemia cells has emerged as an effective approach for AML treatment for patients who are older/unfit for or relapsed from/refractory to current regimens (Isidori A, et al. Frontiers Oncol. 2021). CD123 and CD33, two clinically validated targets in AML, are jointly expressed on blasts and leukemic stem cells (LSC) in >95% of AML patients. However, their expression is heterogenous between subclones and between patients which may impact the efficacy of single-targeting agents in certain patient populations. We recently reported a novel dual-targeting CD33/CD123 NANOBODY® T-cell engager (CD33/CD123-TCE) and demonstrated the anti-leukemia activity of CD33/CD123-TCE in AML with good safety profile in vivo(Dullaers M, et. al, JITC. 2022). Here we showed that CD33/CD123-TCE effectively targets AML blasts and LSC in relapsed AML.

The phosphoinositide 3-kinases (PI3Ks) are critical components of the B-cell receptor (BCR) pathway and have an important role in the pathobiology of chronic lymphocytic leukemia (CLL). Inhibitors of PI3Kd block BCR-mediated cross-talk between CLL cells and the lymph node microenvironment and provide significant clinical benefit to CLL patients. However, the PI3Kd inhibitors applied thus far have limited direct impact on leukemia cell survival and thus are unlikely to eradicate the disease. The use of inhibitors of multiple isoforms of PI3K might lead to deeper remissions. Here we demonstrate that the pan-PI3K/mammalian target of rapamycin inhibitor SAR245409 (voxtalisib/XL765) was more pro-apoptotic to CLL cells—irrespective of their ATM/p53 status—than PI3Ka or PI3Kd isoform selective inhibitors. Furthermore, SAR245409 blocked CLL survival, adhesion and proliferation. Moreover, SAR245409 was a more potent inhibitor of T-cell-mediated production of cytokines, which support CLL survival. Taken together, our in vitrodata provide a rationale for the evaluation of a pan-PI3K inhibitor in CLL patients.

1The present studies were designed to measure the affinity of UP 269‐6, a newly developed angiotensin AT1receptor antagonist, for vascular AT1receptors from normotensive and hypertensive rats and to investigate in vitro, its effects on angiotensin II (AII)‐induced hyperplasia and hypertrophy of vascular smooth muscle cells (VSMC). In addition the in vivo effects of UP 269‐6 on neointimal proliferation in a carotid artery balloon injury in normotensive rats were also investigated.2UP 269‐6 selectively inhibited [125I]‐Sar1‐Ile8‐AII binding to vascular AT1receptors present on VSMC derived from normotensive Wistar rat and from SHR (Ki= 16.6 ± 3.6 nM and 7.5 ± 2.0 nM, respectively). In comparison, losartan and its metabolite, EXP 3174, inhibited [125I‐Sar1‐Ile8‐AII binding to vascular AT1receptors derived from both cell models with Kivalues slightly lower (losartan) and higher (EXP 3174), respectively, than that of UP 269‐6.3AII (1 μM) induced a weak and variable hyperplastic response (4 to 32% increase in cell number) in Wistar rat VSMC after 96 h.4AII (1 μM) induced a time‐dependent increase in cell number in VSMC from SHR. UP 269‐6 inhibited concentration‐dependently this effect with an IC50value of 159 ± 58 nM. Losartan was clearly less potent and EXP 3174 showed nearly the same inhibitory potency, compared to UP 269‐6. UP 269‐6 (1 μm) inhibited nearly completely the action of AII.5AII (500 nM) caused maximal stimulation of protein synthesis in Wistar rat VSMC (117 ± 36%). UP 269‐6, losartan and EXP 3174 totally inhibited this stimulation with IC50values of 28 ± 6 nM, 3504 ± 892 nM and 21±3 nM, respectively.6AII (50 nM) induced maximal stimulation of protein synthesis in SHR VSMC (237 ± 67%). UP 269‐6, losartan and EXP 3174 totally inhibited this stimulation with IC50values of 16 ± 3 nM, 282± 122 nM and 3.3 ± 1.0 nM, respectively.7UP 269‐6 (75 mg kg−1day−1) administered orally in the diet for 20 days induced a 38% reduction in neointimal area and a 36% reduction in neointima/media ratio associated with the intimal thickening induced by carotid artery balloon injury.8In conclusion, UP 269‐6 was shown to be a potent antiproliferative agent both in vitroon AII‐induced hyperplasia and hypertrophy of VSMC derived from normotensive and hypertensive rats, and in vivoupon intimal thickening induced by carotid artery balloon injury in the rat.

Anti-CD38 monoclonal antibodies (mAbs) represent a breakthrough in the treatment of multiple myeloma (MM), yet some patients fail to respond or progress quickly with this therapy highlighting the need for novel approaches. In this study we compared the pre-clinical efficacy of SAR442085, a next generation anti-CD38 mAb with enhanced affinity for activating Fc gamma receptors (FcγR), with first generation anti-CD38 mAb daratumumab and isatuximab. In surface plasmon resonance and cellular binding assays, we found that SAR442085 had higher binding affinity than daratumumab and isatuximab for FcγRIIa (CD32a) and FcγRIIIa (CD16a) receptors. SAR442085 also exhibited better in vitroADCC (antibody dependent cellular cytotoxicity) against a panel of MM cells expressing variable CD38 receptor densities including MM patients’ primary plasma cells. The enhanced ADCC of SAR442085 was confirmed using NK-92 cells bearing low and high affinity FcγRIIIa (CD16a)-158V/F variants. Using MM patients’ primary bone marrow cells, we confirmed that SAR442085 had an increased ability to engage FcγRIIIa, resulting in higher NK cell activation and degranulation against primary plasma cells than pre-existing Fc wild-type anti-CD38 mAbs. Finally, using huFcgRtransgenic mice that express human Fcγ receptors under the control of their human regulatory elements, we demonstrated that SAR442085 had higher NK cell dependent in vivoanti-tumor efficacy and better survival than daratumumab and isatuximab against EL4 thymoma or VK*MYC myeloma cells overexpressing human CD38. These results highlight the preclinical efficacy of SAR442085 and support the current evaluation of this next generation anti-CD38 antibody in phase I clinical development in patients with relapsed/refractory MM.

ABSTRACTNovel therapies are needed for effective treatment of AML. In the relapsed setting, prognosis is very poor despite salvage treatment with chemotherapy. Evidence suggests that leukemic stem cells (LSCs) cause relapse. The cell surface receptor CD123 is highly expressed in blast cells and LSCs from AML patients and is a potential therapeutic target. CD123 cross-over dual-variable domain T-cell engager (CD123-CODV-TCE) is a bispecific antibody with an innovative format. One arm targets the CD3εδ subunit of T-cell co-receptors on the surface of T cells, while the other targets CD123 on malignant cells, leading to cell-specific cytotoxic activity. Here, we describe the preclinical activity of CD123-CODV-TCE. CD123-CODV-TCE effectively binds to human and cynomolgus monkey CD3 and CD123 and is a highly potent T-cell engager. It mediates T-cell activation and T-cell-directed killing of AML cells in vitro. In vivo, CD123-CODV-TCE suppresses AML tumor growth in leukemia xenograft mouse models, where it achieves an effective half-life of 3.2 days, which is a significantly longer half-life compared to other bispecific antibodies with no associated Fc fragment. The in vitro safety profile is as expected for compounds with similar modes of action. These results suggest that CD123-CODV-TCE may be a promising therapy for patients with relapsed/refractory AML.

Correction to: Leukemia (2016) 30, 337–345; doi:10.1038/leu.2015.241; Published 10 November 2015 Following the publication of this article, the authors noted that the following Conflict of Interest statement was missing: EE, MJK and APK have a sponsored research agreement with Sanofi. AVO and CE areemployees of Sanofi.