anti-CD20 IgG1 Research Articles

Anti-CD20 monoclonal antibody therapy in postpartum women with neurological conditions.

Postpartum, patients with multiple sclerosis (MS) and neuromyelitis optica spectrum disorder (NMOSD) have increased risk for disease activity. Anti-CD20 IgG1 monoclonal antibodies (mAb) are increasingly used as disease-modifying therapies (DMTs). Patients may wish to both breastfeed and resume DMT postpartum. This study aimed to determine the transfer of anti-CD20 IgG1 mAbs, ocrelizumab, and rituximab (OCR/RTX), into mature breastmilk and describe maternal and infant outcomes. Fifty-seven cis-women receiving OCR/RTX after 59 pregnancies and their infants were enrolled and followed up to 12M postpartum or 90 days post-infusion. Breastmilk was collected pre-infusion and serially up to 90 days and assayed for mAb concentration. Medical records and patients' questionnaire responses were obtained to assess neurologic, breastfeeding, and infant development outcomes. The median average concentration of mAb in breastmilk was low (OCR: 0.08 μg/mL, range 0.05-0.4; RTX: 0.03 μg/mL, range 0.005-0.3). Concentration peaked 1-7 days post-infusion in most (77%) and was nearly undetectable after 90 days. Median average relative infant dose was <1% (OCR: 0.1%, range 0.07-0.7; RTX: 0.04%, range 0.005-0.3). Forty-three participants continued to breastfeed post-infusion. At 8-12 months, the proportion of infants' growth between the 3rd and 97th World Health Organization percentiles did not differ for breastfed (36/40) and non-breastfed (14/16, p > 0.05) infants; neither did the proportion with normal development (breastfed: 37/41, non-breastfed: 11/13; p > 0.05). After postpartum infusion, two mothers experienced a clinical relapse. These confirm minimal transfer of mAb into breastmilk. Anti-CD20 mAb therapy stabilizes MS activity before conception to the postpartum period, and postpartum treatments appears to be safe and well-tolerated for both mother and infant.

Ocrelizumab in pediatric multiple sclerosis.

Ocrelizumab is a recombinant humanized anti-CD20 monoclonal IgG1, approved by FDA and EMA for adult patients with multiple sclerosis (MS). The data on the efficacy and safety of Ocrelizumab for pediatric MS cases are limited. Here, we describe pediatric relapsing-remitting MS (P-RRMS) cases who were treated with Ocrelizumab as a disease-modifying drug. P-RRMS cases who were started Ocrelizumab below 18 years-of-age and followed-up >12 months with Ocrelizumab treatment were included. The primary end-points were annualized relapse rate (ARR) and magnetic resonance imaging (MRI) activity (new/enlarging T2 lesions and new gadolinium (Gd) enhancing lesions). The secondary end-points were the percentage of patients who remain relapse-free and/or free from Gd enhancing lesions, Expanded Disability Status Scale (EDSS) score, and the safety profile of Ocrelizumab. Of 18P-RRMS cases receiving Ocrelizumab, 10 patients fulfilled the inclusion criteria for our study. The median duration of follow-up under Ocrelizumab was 28,3 months (min: 15 months, max: 46 months). Mean ARR decreased from 2.01 (±0.71) to 0 during the follow-up of Ocrelizumab treatment (P<0.0001). None of the patients had MRI activity during the treatment. Mean EDSS decreased from 1.75 (±1.09) to 1.20 (±0.63) from the initiation of Ocrelizumab to the last follow-up of the patients (P=0.024). None of the patients had serious side effects, except one patient who experienced anaphylaxis. Ocrelizumab can be considered a safe and effective treatment option in highly active P-RRMS.

Abstract PD2-07: Tumor CD73 regulates zoledronate induced TIL accumulation into triple negative breast cancer

Abstract Background: CD73 is a membrane-bound protein that by extracellular adenosine production, regulates immune cell function. Low CD73 expression is associated with better prognosis among triple-negative breast cancer (TNBC) patients. Adjuvant bisphosphonates (BPs, such as zoledronate) improve survival among post-menopausal breast cancer patients, but the mechanism for this is unknown. Since BPs also affect immune cells, we studied 1) whether zoledronate-treatment has an effect on tumor infiltrating lymphocytes (TILs) and 2) whether tumor CD73 expression affects these responses in TNBC tumors. Methods: 4T1 mouse mammary cells, stably expressing non-targeting shRNA (sh-NT, control cells) or sh-CD73 were inoculated into the mammary fat pads of Balb/c mice. The mice were treated with i.p. vehicle or zoledronate (ZOL) each 4th day for total of six times. Additionally, to deplete B-cells, the mice were treated with an anti-CD20 or control IgG antibody. Tumor sizes were assessed with a caliper, TILs were studied with immunostainings. Blood lymphocytes were analyzed with Flow cytometry. Results: Sh-CD73 cells formed significantly smaller tumors, than sh-NT cells. ZOL significantly inhibited the growth of both sh-CD73 and sh-NT tumors, but at sacrifice, this effect of ZOL was more significant against sh-CD73 tumors. ZOL increased the % of CD19+/CD21+ and CD19+/23+ in blood of both mice groups, and this effect was inhibited by anti-CD20 antibody. Although neither treatment alone had an effect, the % of CD3+/CD8+ cells in blood were increased in both mice groups by the combination of ZOL and anti-CD20-antibody. ZOL induced accumulation of B220+, CD4+ and CD8+ TILs into both tumor groups. These TIL effects were reduced with anti-CD20 antibody treatment. Anti-CD20 antibody alone inhibited significantly sh-CD73 tumor growth. Anti-CD20 antibody did not interfere with ZOL inhibition of tumor growth in either group. Conclusions: ZOL has inflammatory effects on blood lymphocytes and TILs, which may be affected by tumor expression of immune system regulating proteins, such as CD73. B cell depletion may further prevent tumor growth, in the context of CD73 inhibition. Further studies are needed to investigate whether B-cell inhibition affects ZOL-induced tumor growth inhibition. Citation Format: Nataliia Petruk, Arafat Siddiqui, Sina Tadayon, Arja Jukkola, Jorma Määttä, Pieta Mattila, Jouko Sandholm, Katri S. Selander. Tumor CD73 regulates zoledronate induced TIL accumulation into triple negative breast cancer. [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD2-07.

Abstract 4179: High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing

Abstract Rituximab-containing treatment regimens are the standard of care for patients with non-Hodgkin’s lymphoma (NHL). However, the majority of patients ultimately experience disease relapse or progression indicating resistance to rituximab therapy. IGM-2323 is an engineered high-affinity, high-avidity anti-CD20 pentameric IgM antibody with an anti-CD3 scFv fused to the joining chain. IGM-2323 offers a novel treatment strategy in NHL through two mechanisms: 1) the recruitment of T cells to kill CD20-expressing tumor cells through T cell dependent cellular cytotoxicity (TDCC) and, 2) complement-dependent cytotoxicity (CDC). We evaluated the activity of IGM-2323 in the presence of rituximab since rituximab can persist in patients after treatment discontinuation, and it can bind to an overlapping epitope on CD20 as IGM-2323. We hypothesized that the high valency of IGM-2323 could displace rituximab, thus enabling potent B cell killing by IGM-2323 even in the presence of high concentrations of rituximab. The affinity of IGM-2323 and its corresponding bivalent anti-CD20 IgG antibody to recombinant human CD20 protein were measured by surface plasmon resonance. IGM-2323 bound to human CD20 with an apparent 300-fold higher binding affinity (KD) and ~100-fold slower off-rate (kdis) than the bivalent anti-CD20 IgG. Human B cell lines with a range of CD20 expression levels, including a CD20-low rituximab-resistant Ramos cell variant, were pre-treated with escalating concentrations of rituximab, and subsequently evaluated in vitro for cell binding, TDCC, and CDC by IGM-2323. At high concentrations of rituximab, which correspond to reported peak serum concentrations (Cmax) found in rituximab-treated patients, IGM-2323 displaced the binding of rituximab on human B cell lines. In contrast, binding of a bispecific CD20xCD3 IgG was severely inhibited by the Cmax of rituximab. In TDCC assays with healthy donor effector T cells, pre-treatment with high concentrations of rituximab only modestly inhibited IGM-2323 activity. Furthermore, only a minor impact to the maximum killing activity (Emax) of IGM-2323 was observed at the Cmax of rituximab. In contrast, rituximab pre-treatment resulted in a distinctly lower Emax of a bispecific CD20xCD3 IgG. Live cell imaging of CDC kinetics was utilized to quantify the extent of CDC by IGM-2323 with or without rituximab. Pre-treatment with rituximab enhanced CDC of IGM-2323 compared to single agent activity. Our preclinical data indicate that IGM-2323 maintains activity in the presence of rituximab. IGM-2323 is currently being studied in a phase 1 clinical trial in relapsed/refractory NHL, where it has been generally well tolerated, with both complete and partial responses observed (NCT04082936). Clinical studies will continue to evaluate these findings, including the treatment of patients with circulating serum levels of rituximab. Citation Format: Kevin C. Hart, Kathryn Logronio, Mandy Li, Poonam Yakkundi, Marigold Manlusoc, Keyu Li, Paul R. Hinton, Dean Ng, Maya K. Leabman, Genevive Hernandez, Thomas Manley, Angus M. Sinclair, Stephen F. Carroll, Bruce A. Keyt, Maya F. Kotturi. High valency of IGM-2323, a CD20xCD3 IgM bispecific T cell engager, displaces rituximab binding and induces potent B lymphoma cell killing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4179.

Donor B Cells Alter Donor Neutrophil Behaviour and Protect from Lethality During Lung Allograft Reperfusion in Mice

<h3>Purpose</h3> We showed that donor B cell depletion causes mortality in a C57BL/10 (B10, H-2^b)-to-C57BL/6 (B6, H-2^b) minor alloantigen-mismatched mouse orthotopic lung transplant model with prolonged graft storage to induce ischemia-reperfusion injury (Kawashima et al. 2021 ISHLT abstract). This finding prompted us to investigate possible mechanisms by which donor B cells might augment lung injury and mortality. <h3>Methods</h3> We performed B10-to-B6 left lung transplants with prolonged (6h at 4°C followed by 45min at 37°C and 15min anastomosis time) antecedent storage using congenic donors and recipients. Donors received anti-CD20 antibody or IgG control on day -2 (Fig 1A). Necropsies were performed 1 hour after reperfusion or upon earlier recipient death. Allograft wet/dry weight ratio (W/D ratio) was assessed. Flow cytometry was used to enumerate myeloid cell populations in donor and recipient lungs given B cells and neutrophil interaction was reported elsewhere. Two-photon microscopy of precision-cut lung slices was used to observe cellular behaviour. <h3>Results</h3> Donor anti-CD20 treatment was associated with early postoperative death (p=NS), consistent with our previous report (Fig 1B). The W/D ratio of transplanted left lung was higher in the anti-CD20 group compared with normal lung control (Fig 1C, p=0.01). Anti-CD20 treatment depleted B cells from donor lungs and resulted in decreased donor neutrophils post-transplant (Fig 1D, p=0.02). Recipient myeloid cell numbers did not differ between the groups (not shown). An increase in neutrophil motility was observed in donor lungs from anti-CD20-treated mice (Fig 1E, p<0.01). <h3>Conclusion</h3> Our results suggest that altered donor neutrophil function triggered by B cell depletion may contribute to acute lung injury leading to death in a subset of recipients. Further investigation is now underway.

A Third Anti-Sars-Cov2 mRNA Dose Does Not Overcome the Pejorative Impact of Anti-CD20 Therapy and/or Low Immunoglobulin Level in CLL/Lymphoma Patients

Introduction: Patients with lymphoma and chronic lymphocytic leukemia (CLL) share immune-deficiencies due to the biological features of these diseases per se and to their treatments. They are at risk to develop severe and/or prolonged forms of Covid-19. The efficacy of vaccination against COVID in lymphoma/CLL patients also raises specific concerns: Antibody response to mRNA COVID-19 vaccine was shown to be negatively affected by CLL stage and its treatments, especially in case of previous administration of anti-CD20 antibodies (Herishanu et al). Therefore, the addition of a third dose of vaccine in immunosuppressed patients is currently recommended in France.Methods: To analyse the determinants of the antibody response after anti-SARS-Cov2 mRNA vaccines (Pfizer or Moderna), we conducted a retrospective monocentric study among adults with a past or current lymphoma/CLL who underwent serology 2 weeks or more after 2 or 3 previous injections. The decision of a third dose was at the discretion of each physician. Data were extracted from the patients' medical charts on their demographics, lymphoma history and detailed treatments, vaccinations and biological parameters (immunoglobulin (Ig) G dosage, lymphocytic, B-cell and T-cell counts) and serology (Elecsys ® Anti-SARS-CoV-2 S). Statistical tests were two-tailed and p-values < 0.05 were considered significant. Multivariable analysis was conducted using independent variables having univariate significance below 0.1.This study was conducted in accordance with the Declaration of Helsinki, and approved by the ethics committee of our institution.Results: Ninety-one patients with non-Hodgkin's lymphomas (NHL) (n=48), CLL (32) or Hodgkin's lymphoma (11) were enrolled. With a median interval since last dose of 47 days (range 15-125), 48 patients (53%) had a negative serology (Table). Gender and age were not associated with antibody response. The proportion of seronegativity was 57% among patients with B-cell NHL, and 41% among those with CLL. Among the biological variables reflecting immune deficiency, lymphocytopenia (<1.5G/L), low B-cell counts (<0.2G/L) and IgG levels (<6g/L) were significantly associated with a higher risk of seronegativity with odds-ratios (OR, [95% confidence interval]) of 5.1 [1.8-15.3], p<7x10 -4 , 15.0 [3.0-147.9], p<7x10 -5, and 15.3 [3.7-93.0], p<9x10 ⁻6 respectively).Patients under watch and wait attitude and those who did not have a lymphoma/CLL treatment since at least 12 months before vaccination had a much lower risk of negative serology (OR: 0.08 [<0.01 ; 0.4], p< 2.10 -4). Among lymphoma/CLL therapies, chemotherapy overall or targeted therapy with BTK inhibitors or Venetoclax were not significantly associated with a lower risk of negative serology. In contrast, the administration of anti-CD20 therapy during the year before first dose of vaccine was associated with a higher risk of negative serology (OR: 4.5 [1.7; 12.1], p<8.10 -4). Of note, this treatment was also significantly associated with both lymphocytopenia and low B-cell counts. There was no association between the number of vaccine doses and the risk of negative serology, 59% of the patients who received 3 doses remained seronegative.A multivariable analysis associating IgG level and treatment history showed that negative serology is significantly associated with a low level of IgG (OR: 25.74 [5.58; 201.14], p < 10 -3) and anti-CD20 treatment (OR: 28.70 [4.14, 382.60], p = 3x10 -3).Conclusion: Overall, previous anti-CD20 therapy and low IgG levels are the main independent factors associated with a lack of serological response after anti-SARS-Cov2 mRNA vaccine. Administration of a third vaccine does not overcome their pejorative impact. This should contribute to the elaboration of guidelines for the management of lymphoma/CLL patients during the Covid-19 era. In particular, in all non-critical clinical situation, SARS-CoV-2 vaccination should be proposed before the onset of lymphoma/CLL therapy. Meanwhile, individuals with CLL/lymphoma should receive the Covid-19 vaccine, be informed that they are unlikely to be protected and continue social distancing and adhere to other proven mitigation strategies. Systematic vaccination of their proxies and hospital workers should also benefit directly to patients. [Display omitted] DisclosuresRigaudeau: Takeda: Membership on an entity's Board of Directors or advisory committees.

Efficacy and Safety of Recombinant Human-Mouse Chimeric Anti-CD20 Monoclonal Antibody (SCT400) Combined with CHOP in Patients with Treatment-Naïve Diffuse Large B-Cell Lymphoma: A Multicenter, Randomized, Single-Blind, Parallel Active-Controlled, Phase III Study

Background:SCT400 is a recombinant, human-mouse chimeric anti-CD20 IgG1 monoclonal antibody and has the same variable regions and antigen-binding site as rituximab. SCT400 has the heavy and κ light chain constant regions of human IgG1 allotype G1m (1,17), which is common in Asians. There is only one amino acid difference between SCT400 and rituximab (V219A in the CH1 domain of the heavy chain). The phase Ⅱ study showed that pharmacokinetics, pharmacodynamics and safety of SCT400 are equivalent to rituximab in patients with CD20-positive non-Hodgkin lymphoma.Objectives:This phase III study aimed to evaluate the safety and efficacy of SCT400 plus cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) compared with rituximab plus CHOP in patients with treatment-naïve diffuse large B-cell lymphoma (DLBCL) (ClinicalTrials.gov, identifier: NCT02772822).Methods:In this multicenter, randomized, single-blind, parallel active-controlled, non-inferiority, phase III study, patients were enrolled from 37 centers in China. Eligible patients were aged 18～75 years with histologically confirmed CD20-positive, treatment-naïve DLBCL; international prognostic index (IPI) 0～2; an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0～2. Patients were randomly assigned in a 2:1 ratio to receive either SCT400 plus CHOP (S-CHOP) or rituximab plus CHOP (R-CHOP) every 21 days cycle treatment for six cycles.The primary endpoint was objective response rate (ORR) after six cycles of therapy, assessed by an independent review committee, with a non-inferiority margin of -12%. The secondary endpoints were complete response rate (CRR), progression-free survival (PFS), overall survival (OS), and safety.Results:Between October 19, 2016 and July 13, 2018, 534 patients were screened and 364 eligible patients were randomized to either the S-CHOP group (n=243) or R-CHOP group (n=121). Patient demographics and disease characteristics at baseline were well balanced between the two treatment groups.In the per protocol set (PPS), the best ORRs within six cycles of treatment were 94.5% (95% confidence interval [CI], 90.8% to 97.0%) and 94.1% (95%CI, 88.2% to 97.6%) in the S-CHOP and R-CHOP groups respectively, with an intergroup difference of 0.4% (95%CI, -4.7% to 5.6%, P=0.6569) (Figure 1A). The 95%CI lay on the positive side of the prespecified non-inferiority margin of -12%, meeting the criterion for non-inferiority. The results of using the full analysis set (FAS) were consistent with the primary efficacy analysis in the PPS. No significant differences were observed in the secondary efficacy endpoints, in either the PPS or the FAS (Figure 1B and Figure 2).There were no significant differences were observed in ≥1 adverse event (AE, 97.9% vs. 99.2%), grade≥3 AE (85.2% vs. 86.0%), serious AE (35.4% vs. 38.8%), treatment discontinuation due to AE (7.8% vs.12.4%) between S-CHOP and R-CHOP groups, respectively (Table 1).AEs of special interest occurred in 63.8% of patients in the S-CHOP group and in 59.5% of patients in R-CHOP group, including infection (46.5% vs. 46.3%), infusion-related reaction (20.2% vs. 17.4%), cardiotoxicity (17.7% vs. 11.6%), hepatitis B virus reactivation (1.2% vs. 3.3%), ileus and enterobrosis (1.2% vs. 0.8%), tumor lysis syndrome (0.0% vs. 0.8%) (Table 1).A total of 51 deaths were reported in the S-CHOP group (n=35, 14.4%) and R-CHOP group (n=16, 13.2%), and 10 deaths were due to AE (S-CHOP group: n=7, 2.9%; R-CHOP group: n=3, 2.5%) (Table 1).After treatment, study-drug related anti-drug antibodies (ADAs) were detected in 11(10.9%) patients in S-CHOP group and in 8(16.0%) patients in R-CHOP group (Table 1).Conclusion:SCT400 plus CHOP showed non-inferiority of efficacy to rituximab plus CHOP in patients with treatment-naïve DLBCL. The safety and immunogenicity profiles of SCT400 were comparable with rituximab, with no new treatment-related AE occurred. SCT400 could be a therapeutic option for DLBCL.Funding source:This study was supported by the sponsor, Sinocelltech Ltd., and by grants from the China National Major Project for New Drug Innovation (No. 2018ZX09736002 and No. 2017ZX09304015).Conflicts of interest:Liangzhi Xie is an employee of Sinocelltech Ltd. and has ownership interests in the company. All other authors declare no conflicts of interest. [Display omitted] DisclosuresHu: Astellas Pharma, Inc.: Research Funding. Xie: Sinocelltech Ltd.: Current Employment, Current equity holder in publicly-traded company.

The interplay of protein engineering and glycoengineering to fine-tune antibody glycosylation and its impact on effector functions.

The N-glycan pattern of an IgG antibody, attached at a conserved site within the fragment crystallizable (Fc) region, is a critical antibody quality attribute whose structural variability can also impact antibody function. For tailoring the Fc glycoprofile, glycoengineering in cell lines as well as Fc amino acid mutations have been applied. Multiple glycoengineered Chinese hamster ovary cell lines were generated, including defucosylated (FUT8KO), α-2,6-sialylated (ST6KI), and defucosylated α-2,6-sialylated (FUT8KOST6KI), expressing either a wild-type anti-CD20 IgG (WT) or phenylalanine to alanine (F241A) mutant. Matrix-assisted laser desorption ionization-time of flight mass spectrometry characterization of antibody N-glycans revealed that the F241A mutation significantly increased galactosylation and sialylation content and glycan branching. Furthermore, overexpression of recombinant human α-2,6-sialyltransferase resulted in a predominance of α-2,6-sialylation rather than α-2,3-sialylation for both WT and heavily sialylated F241A antibody N-glycans. Interestingly, knocking out α-1,6-fucosyltransferase (FUT8KO), which removed core fucose, lowered the content of N-glycans with terminal Gal and increased levels of terminal GlcNAc and Man5 groups on WT antibody. Further complement-dependent cytotoxicity (CDC) analysis revealed that, regardless of the production cells, WT antibody samples have higher cytotoxic CDC activity with more exposed Gal residues compared to their individual F241A mutants. However, the FUT8KO WT antibody, with a large fraction of bi-GlcNAc structures (G0), displayed the lowest CDC activity of all WT antibody samples. Furthermore, for the F241A mutants, a higher CDC activity was observed for α-2,6- compared to α-2,3-sialylation. Antibody-dependent cellular cytotoxicity (ADCC) analysis revealed that the defucosylated WT and F241A mutants showed enhanced in vitro ADCC performance compared to their fucosylated counterparts, with the defucosylated WT antibodies displaying the highest overall ADCC activity, regardless of sialic acid substitution. Moreover, the FcγRIIIA receptor binding by antibodies did not always correspond directly with ADCC result. This study demonstrates that glycoengineering and protein engineering can both promote and inhibit antibody effector functions and represent practical approaches for varying glycan composition and functionalities during antibody development.

Abstract 231: Evaluation of pharmacologic mechanisms to overcome IgG1 antibody (Ab) resistance via quantitative systems pharmacology (QSP) modeling of antibody-dependent cell mediated cytotoxicity (ADCC)

Abstract Novel therapies that enhance ADCC have the potential to overcome Rituximab (RTX) resistance in lymphoma, which can occur due to e.g. CD20 loss, immunogenicity-induced reduction in RTX exposure, or SNPs resulting in lower CD16:Fc affinity. Nonlinear interactions between effector cells (ECs), drug, and target cell (TC) factors in ADCC, however, complicate the prediction of the net effect of potential therapeutic strategies that modulate one or more factors such as CD16 expression ([CD16]) on ECs, CD16:Fc binding affinity, or intrinsic killing propensity (g).We have developed a QSP model of the molecular-level binding reactions and cell-cell interactions governing ADCC using the anti-CD20 IgG1 antibody RTX in lymphoma as a case study. This model takes as inputs [CD16] on ECs, g, Ab Fc:CD16 binding affinity, [RTX], RTX:CD20 affinity, and [CD20] on TCs and predicts the degree of ADCC killing of tumor cells after RTX exposure. Simulations can then be used to estimate how much increase in an input parameter a potential RTX combination partner must provide to compensate for a given mechanism of RTX resistance (MoRR). The model has been successfully calibrated to ex vivo [RTX]-ADCC assays in SUDHL4 and Z138 cell lines (Herter, Mol Cancer Ther, 2013). The model and estimated parameter set well described the observed [RTX]-dependent %ADCC in both cell lines with ECs (PBMCs) from two donors with V158 and F158 CD16 SNP variants. The table below provides the model predictions of the fold increase in model parameters required to offset various MoRRs. For example, a 10-fold loss of [CD20] on TCs is predicted to cause a 100*(1 - 0.16) = 84% drop in ADCC activity, which can be overcome by a 7.8-fold increase in [CD16] on ECs. We have developed a mechanism-based simulation tool which can be used to predict the ability of novel ADCC-enhancing agents to overcome different mechanisms of IgG1 Ab resistance. Mechanism of RTX resistance (MoRR)ADCC fold change due to MoR(90% CI)Fold change in parameter required to restore ADCC (90% CI)CD16 expression on effector cells [CD16]CD16:Fc binding affinity kon16NK killing propensity g10x loss of CD20 on tumor0.16 (0.13,0.20)7.8 (6.3,9.2)10.6 (10.4,10.9)7.4 (6.1,8.7)10x loss of RTX exposure0.17(0.14,0.21)7.0(5.7,8.1)9.36(9.35,9.37)6.9(5.7,8.1)10x decrease in CD16:Fc affinity0.16(0.13,0.20)7.4(6.1,8.7)10(10,10)7.4(6.1,8.6) Citation Format: Kaitlyn E. Johnson, Maria Veronica Ciocanel, Josua Aponte, Nicolas Bajeux, Fanwang Meng, Dean Bottino. Evaluation of pharmacologic mechanisms to overcome IgG1 antibody (Ab) resistance via quantitative systems pharmacology (QSP) modeling of antibody-dependent cell mediated cytotoxicity (ADCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 231.

Generating Informative Sequence Tags from Antigen-Binding Regions of Heavily Glycosylated IgA1 Antibodies by Native Top-Down Electron Capture Dissociation.

Immunoglobulins A (IgA) include some of the most abundant human antibodies and play an important role in defending mucosal surfaces against pathogens. The unique structural features of the heavy chain of IgA subclasses (called IgA1 and IgA2) enable them to polymerize via the joining J-chain, resulting in IgA dimers but also higher oligomers. While secretory sIgA oligomers are dominant in milk and saliva, IgAs exist primarily as monomers in serum. No method currently allows disentangling the millions of unique IgAs potentially present in the human antibody repertoire. Obtaining unambiguous sequence reads of their hypervariable antigen-binding regions is a prerequisite for IgA identification. We here report a mass spectrometric method that uses electron capture dissociation (ECD) to produce straightforward-to-read sequence ladders of the variable parts of both the light and heavy chains of IgA1s, in particular, of the functionally critical CDR3 regions. We directly compare the native top-down ECD spectra of a heavily and heterogeneously N- and O-glycosylated anti-CD20 IgA1, the corresponding N-glycosylated anti-CD20 IgG1, and their Fab parts. We show that while featuring very different MS1 spectra, the native top-down ECD MS2 spectra of all four species are nearly identical, with cleavages occurring specifically within the CDR3 and FR4 regions of both the heavy and light chain. From the sequence-informative ECD data of an intact glycosylated IgA1, we foresee that native top-down ECD will become a valuable complementary tool for the de novo sequencing of IgA1s from milk, saliva, or serum.

Rituximab Induced Interstitial Lung Disease Diagnosis, Treatment Outcome, and Risk’s Factor, a Place for Transbronchial Pulmonary Cryobiopsy

Rituximab (RTX) is a mouse/human chimeric anti-CD20 IgG1 monoclonal antibody, approved in late 1998 by the FDA. Effectively used as a single agent or combined with a chemotherapy regimen to treat lymphoma, RTX is a significant step forward in the arsenal treatment of idiopathic thrombocytopenic purpura, systemic lupus erythematous, rheumatoid arthritis, and autoimmune hemolytic anemia. Side effects of RTX are commonly seen during the first infusion in up to 50% of patients and include fever, chills, and rigors. These side effects are generally transient and related to the tumor burden, probably due to a greater degree of complement activation and proinflammatory cytokine release. Severe lung toxicity like cryptogenic organizing pneumonia, pneumonitis, and interstitial lung diseases are infrequent, with most of the knowledge coming from case reports.

Rituximab-specific DNA aptamers are able to selectively recognize heat-treated antibodies.

The monoclonal anti-CD20 IgG1 antibody rituximab is used as a first-line treatment for B cell lymphoma. Like all therapeutic antibodies, it is a complex protein for which both safety and efficacy heavily depend on the integrity of its three-dimensional structure. Aptamers, short oligonucleotides with a distinct fold, can be used to detect minor modifications or structural variations of a molecule or protein. To detect antibody molecules in a fold state occurring prior to protein precipitation, we generated DNA aptamers that were selected for extensively heat-treated rituximab. Using the magnetic bead-based systematic evolution of ligands by exponential enrichment (SELEX), we obtained six DNA aptamer sequences (40-mers) specific for 80°C heat-treated rituximab. In silico fold prediction and circular dichroism analysis revealed a G-quadruplex structure for one aptamer, while all others exhibited a B-DNA helix. Binding affinities ranging from 8.8–86.7 nM were determined by an enzyme-linked apta-sorbent assay (ELASA). Aptamers additionally detected structural changes in rituximab treated for 5 min at 70°C, although with lower binding activity. Notably, none of the aptamers recognized rituximab in its native state nor did they detect the antibody after it was exposed to lower temperatures or different physical stressors. Aptamers also reacted with the therapeutic antibody adalimumab incubated at 80°C suggesting similar aptamer binding motifs located on extensively heat-treated IgG1 antibodies. Within this work, we obtained the first aptamer panel, which is specific for an antibody fold state specifically present prior to protein aggregation. This study demonstrates the potential of aptamer selection for specific stress-based protein variants, which has potential impact for quality control of biopharmaceuticals.

Anti-CD20 rituximab IgG1, IgG3, and IgG4 but not IgG2 subclass trigger Ca2+ mobilization and cytotoxicity in human NK cells.

NK cell-mediated Ab-dependent cellular cytotoxicity (ADCC) is increasingly recognized to play an important role in cancer immunotherapy, transplant rejection, and autoimmunity. However, several aspects of the molecular interactions of IgG subclasses with the Fc-gamma receptor IIIA (FcγRIIIA)/CD16a expressed on NK cells remain unknown. The aim of the current study was to further analyze the role of IgG subclasses and FCGR3A V158F single nucleotide polymorphism (SNP) on Ca2+ signaling and NK cell-mediated ADCC against Daudi target cells in vitro. NK cells were isolated from donors with different FCGR3A SNP. The affinity of rituximab IgG subclasses to CD20 expressed on Daudi cells showed similar dissociation constant as tested by flow cytometry. Induction of Ca2+ signaling, degranulation, intracellular cytokine production, and ADCC was demonstrated for IgG1 and IgG3, to a lesser degree also for IgG4, but not for IgG2. Compared to NK cells carrying the low-affinity (FF) variant for the FCGR3A V158F SNP, binding of IgG1 and IgG3 to NK cells carrying the high-affinity (VV) and VF SNP variants was two- to threefold higher. Variations of FCGR3A SNP among the eight tested donors (1 VV, 3FF, and 4VF) revealed no significant differences of Ca2+ signaling and degranulation; however, ADCC was somewhat weaker in donors with the low-affinity FF variation. In conclusion, this is the first study correlating Ca2+ signaling and NK cell-mediated ADCC triggered by the four IgG subclasses with the FCGR3A V158F SNP. Our findings indicate important differences in the interactions of IgG subclasses with FcγRIIIA/CD16a but no major impact of FCGR3A SNP and may therefore help to better correlate the functional properties of particular engineered therapeutic antibodies in vitro with individual differences of their clinical efficacy.

Lymphoma cell-killing activity and cytokine release by CD20-directed bispecific IgM antibody-based T-cell engager (IGM-2323).

e15007 Background: Bispecific antibodies which tether T-cells to cancer cells, and additionally activate T-cell mediated killing, have shown promise in treating B-cell malignancies. Dose intensity, however, is limited by cytokine release from the activated T-cells. Side effects include fever, hypotension, and hypoxia. Methods: A novel type of bispecific antibody (IGM-2323) was constructed using the pentameric IgM framework. Recombinant IgM heavy chains and kappa light chains with high affinity variable domains derived from an anti-CD20 IgG, were co-expressed with a J-chain fused to anti-CD3 single chain Fv domain. IGM-2323 has 10 binding domains for CD20, and one binding domain for CD3. Results: IGM-2323 binds to the CD20 antigen with &gt; 1000-fold increased avidity relative to an IgG antibody format. IGM-2323 in human cell cultures shows highly potent T cell dependent cytotoxicity (EC50 20 pM), even on cells with very low cell surface expression of CD20, rituximab-resistant lymphoma cell lines, and patient derived CLL cells. Significantly, IGM-2323 exhibits vastly reduced cytokine release, with equivalent T cell dependent killing of CD20-expressing cancer cells, as compared to corresponding IgG-based T cell bispecifics made with the same binding domains. IGM-2323 mediated killing can occur at low T-cell/cancer cell ratios, as low as (1:5). In addition, IGM-2323 mediates complement dependent cytotoxicity (CDC) of CD20-expressing cells with &gt; 100-fold higher potency than IgG. IgM-based bispecific (anti-CD20 x anti-CD3) completely depletes circulating B cells in cynomolgus monkeys at doses of &gt; 300 µg per kg. Furthermore, durable depletion of B cells in spleen and lymphoid tissues was noted with multiple doses of &gt; 1 mg/kg. Importantly, in these studies no observable adverse effects were seen, despite repeated doses at up to 25 mg/kg (the highest dose tested). Low levels of transiently increased circulating IL-6 and no increased levels of circulating TNF-α and IFN-γ were observed in these primate studies. Conclusions: These data indicate that IgM-based bispecifics can induce T cell engagement and very potent cytotoxicity that can be dissociated from cytokine release syndrome in the primate model. These preclinical data demonstrate the potential for broad application of this novel modular IgM-based bispecific antibody format. A Phase I dose-escalation study of IGM-2323 in patients with relapsed/refractory Non-Hodgkin’s lymphoma has been initiated (NCT04082936) and is currently enrolling patients.

Effect of the total galactose content on complement-dependent cytotoxicity of the therapeutic anti-CD20 IgG1 antibodies under temperature stress conditions

The degree of monoclonal antibody galactosylation is known to affect complement-dependent cytotoxicity (CDC) activity by affecting C1q binding, suggesting that galactose is associated with CDC bioactivity. However, whether this association also exists under temperature stress conditions is not known. This study highlights the impact of variations in the terminal galactose content of an anti-CD20 monoclonal antibody on CDC bioactivity under high-temperature stress conditions compared with storage conditions at 2–8 °C. Drug product samples with a total galactose content of >38% showed stable CDC bioactivity at higher temperatures (45 °C), while those with 16% galactose content showed reduced CDC activity.

JNJ-64457107, a CD40 Agonist, Induces Cell Death in BCL6hiIRF4neg GCB Subtype of DLBCL

CD40 is a member of the TNF receptor family that is expressed in multiple tumor types and normal cells including antigen presenting cells (APC), endothelium and platelets. CD40-CD40L signaling is one of the pivotal mechanisms essential for robust antigen presentation and adaptive immunity. JNJ-64457107 (JNJ-107) is an anti-CD40 IgG1 agonistic antibody that is currently in a Phase 1 clinical trial (NCT02829099). JNJ-107/ADC-1013 induced significant anti-tumor activity and immunological memory (Mangsbo 2015). It was also reported that a CD40 agonist, SGN-40, induced direct cytotoxicity in diffuse large B cell lymphoma (DLBCL) cell lines (Burlington 2011), and clinical responses have been noted in this indication (Advani 2009). However, not all DLBCL patients and DLBCL cell lines respond to SGN-40. Thus, a patient selection strategy in B cell malignancies may be beneficial. Here, we investigated the mechanism of action and potential biomarkers of response to JNJ-107 in DLBCL.Here, we show that JNJ-107 induced dose-dependent APC activation measured by upregulation of co-stimulatory molecules CD86, CD54, HLA-DR and CD23 on peripheral B cells in ex vivo whole blood and in vitro generated dendritic cells by flow cytometry. The highest APC activation was at 0.1-5 µg/ml of JNJ-107. We also found that JNJ-107 induced cell death of CD40 positive DLBCL cell lines representing both, germinal center B-cell (GCB) and activated B-cell (ABC) subtypes at similar doses. Cell death was measured by the Cell Titer-Glo assay and confirmed by staining with PI/AnnexinV. JNJ-107 at 1 µg/ml induced cell death (in 30-90% of cells) in 11/20 DLBCL cell lines (called “sensitive”) after 4 days of treatment, with 2 GCB lines (BJAB and SU-DHL4) showing >90% cell death. No DLBCL cell line proliferation was observed in response to JNJ-107.CD40 signals through the NF-kB pathway in DLBCL. We investigated, if basal expression of NF-kB signaling components predicts responses to JNJ-107. First, we assessed activation of the NF-kB pathway in DLBCL lines by Western blot before and after treatment with JNJ-107. We used p65 and p52 as markers of canonical and non-canonical NF-kB activation, respectively. We found that JNJ-107 predominantly activated non-canonical NF-kB signaling in DLBCL cell lines by inducing p100 cleavage and release of p52 (Figure 1). A lower rate of p52 induction was observed in JNJ-107 “sensitive” lines that had constitutive expression of p52 (Pfeiffer, OCI-Ly7). Thus, we did not observe strong correlation between p52 induction and cell death in response to JNJ-107.BCL6 and IRF4 are markers of cell of origin in DLBCL. BCL6 and IRF4 are constitutively expressed in GCB and ABC subtypes, respectively. Interestingly, “sensitive” GCB lines had higher BCL6 expression than resistant lines. BCL6 protein was rapidly degraded (within 16h) in “sensitive” GCB DLBCL lines stimulated with JNJ-107. BCL6 is a transcriptional repressor that is regulated by many factors including IRF4. IRF4 is induced downstream of CD40, and directly represses BCL6 expression by binding to its promoter (Saito 2007). Consistent with constitutive activation of NF-kB, ABC DLBCL lines constitutively expressed IRF4. Surprisingly, several GCB lines also constitutively expressed IRF4 and were unable to further upregulate IRF4 in response to JNJ-107. The latter lines showed a lower degree of cell death in response to JNJ-107 compared to lines negative for IRF4 expression (except Pfeiffer).In summary, APC activation in whole blood, direct cytotoxicity and non-canonical NF-kB activation in DLBCL cell lines were seen with CD40 agonist, JNJ-107. GCB cell lines with high BCL6 expression and negative for IRF4 (BCL6hiIRF4neg) were more sensitive to JNJ-107 induced cell death. Based on these findings, GCB DLBCL patients with functional CD40 signaling in the tumor cells (BCL6hiIRF4neg phenotype) may show enhanced anti-tumor responses.Figure 1. JNJ-107 potently induces non-canonical NF-kB signaling in DLBCL cell lines. DLBCL lines were treated with 0.1 µg/ml JNJ-107 for 15 min, then 5 µg/ml cross-linker, IgG F(ab')2 for 16h. p65 and p52 fold induction was determined by Western blot of whole lysates. Representative data of 2 independent experiments are shown. [Display omitted] DisclosuresRusbuldt:Janssen R&D: Employment. Smith:Janssen R&D: Employment. Balasubramanian:Janssen Research & Development: Employment, Equity Ownership. Borzillo:Janssen R&D: Employment. Alvarez Arias:Janssen R&D: Employment.

Development of a new high-affinity human antibody with antitumor activity against solid and blood malignancies.

mAbs have emerged as a promising strategy for the treatment of cancer. However, in several malignancies, no effective antitumor mAbs are yet available. Identifying therapeutic mAbs that recognize common tumor antigens could render the treatment widely applicable. Here, a human single-chain variable fragment (scFv) antibody library was sequentially affinity selected against a panel of human cancer cell lines and an antibody fragment (named MS5) that bound to solid and blood cancer cells was identified. The MS5 scFv was fused to the human IgG1 Fc domain to generate an antibody (MS5-Fc fusion) that induced antibody-dependent cellular cytotoxicity and phagocytosis of cancer cells by macrophages. In addition, the MS5-Fc antibody bound to primary leukemia cells and induced antibody-dependent cellular cytotoxicity. In the majority of analyzed cancer cells, the MS5-Fc antibody induced cell surface redistribution of the receptor complexes, but not internalization, thus maximizing the accessibility of the IgG1 Fc domain to immune effector cells. In vitro stability studies showed that the MS5-Fc antibody was stable after 6 d of incubation in human serum, retaining ∼60% of its initial intact form. After intravenous injections, the antibody localized into tumor tissues and inhibited the growth of 3 different human tumor xenografts (breast, lymphoma, and leukemia). These antitumor effects were associated with tumor infiltration by macrophages and NK cells. In the Ramos B-cell lymphoma xenograft model, the MS5-Fc antibody exhibited a comparable antitumor effect as rituximab, a chimeric anti-CD20 IgG1 mAb. These results indicate that human antibodies with pan-cancer abilities can be generated from phage display libraries, and that the engineered MS5-Fc antibody could be an attractive agent for further clinical investigation.-Sioud, M., Westby, P., Vasovic, V., Fløisand, Y., Peng, Q. Development of a new high-affinity human antibody with antitumor activity against solid and blood malignancies.

Effect of Fc-γ Receptor Polymorphism on Rituximab-Mediated B Cell Depletion in ABO-Incompatible Adult Living Donor Liver Transplantation.

The affinity of IgG Fc receptor (FcγR) for rituximab, an anti-CD20 IgG1, differs based on single-nucleotide polymorphisms (SNPs) in FcγRs. This study aimed to explore the effect of such SNPs on clinical response to rituximab and outcomes in patients of ABO-incompatible (ABOi) living donor liver transplantation (LDLT). SNPs of FCGR2A[131H/R] and FCGR3A[158F/V], alleles encoding FcγR, were identified in 20 patients desensitized with rituximab before ABOi LDLT. The effect of these SNPs on B cell elimination and outcomes was analyzed in the patients. The isoform encoded by FCGR2A[131H/H] had a higher affinity for IgG1, and accordingly, the effects of rituximab on B cells were more profound in individuals with FCGR2A[131H/H] than in individuals with FCGR2A[131H/R or R/R]. Specifically, the time to B-cell reappearance in the peripheral blood was significantly delayed, and total serum IgM levels were significantly lower early after LDLT in individuals with FCGR2A[131H/H], even though these SNPs did not significantly affect the reduction of antiblood group A/B antibodies. The incidence of blood stream infection was also significantly higher in individuals with FCGR2A[131H/H], and this SNP was associated with poor prognosis. Despite no significant effect of FCGR3A[158F/V] on survival after ABOi liver grafts, the incidence of infection was significantly higher in individuals with FCGR3A[158F/V or F/F] than in individuals with FCGR3A[158V/V]. Our findings indicate FCGR SNPs influence the effect of rituximab on B-cell depletion and are possibly predisposing factors for infectious complications after ABOi LDLT. This study will be a good foundation for further studies on larger cohorts.

Specific Conjugation of the Hinge Region for Homogeneous Preparation of Antibody Fragment-Drug Conjugate: A Case Study for Doxorubicin-PEG-anti-CD20 Fab' Synthesis.

Conventional preparation strategies for antibody-drug conjugates (ADCs) result in heterogeneous products with various molecular sizes and species. In this study, we developed a homogeneous preparation strategy by site-specific conjugation of the anticancer drug with an antibody fragment. The model drug doxorubicin (DOX) was coupled to the Fab' fragment of anti-CD20 IgG at its permissive sites through a heterotelechelic PEG linker, generating an antibody fragment-drug conjugate (AFDC). Anti-CD20 IgG was digested and reduced specifically with β-mercaptoethylamine to generate the Fab' fragment with two free mercapto groups in its hinge region. Meanwhile, DOX was conjugated with α-succinimidylsuccinate ω-maleimide polyethylene glycol (NHS-PEG-MAL) to form MAL-PEG-DOX, which was subsequently linked to the free mercapto containing Fab' fragment to form a Fab'-PEG-DOX conjugate. The dual site-specific bioconjugation was achieved through the combination of highly selective reduction of IgG and introduction of heterotelechelic PEG linker. The resulting AFDC provides an utterly homogeneous product, with a definite ratio of one fragment to two drugs. Laser confocal microscopy and cell ELISA revealed that the AFDC could accumulate in the antigen-positive Daudi tumor cell. In addition, the Fab'-PEG-DOX retained appreciable targeting ability and improved antitumor activity, demonstrating an excellent therapeutic effect on the lymphoma mice model for better cure rate and significantly reduced side effects.

Anti-CD20 Immunoglobulin G Radiolabeling with a 99mTc-Tricarbonyl Core: In Vitro and In Vivo Evaluations.

In recent years, the diagnostic and therapeutic uses of radioisotopes have shown significant progress. Immunoglobulin (Ig) appears to be a promising tracer, particularly due to its ability to target selected antigens. The main objective of this study is to optimize and assess an Ig radiolabeling method with Technetium 99m (99mTc), an attractive radioelement used widely for diagnostic imaging. Monoclonal anti-CD20 IgG was retained to study in vitro and in vivo radiolabeling impact. After IgG derivatization with 2-iminothiolane, IgG-SH was radiolabeled by an indirect method, using a 99mTc-tricarbonyl core. Radiolabeling stability was evaluated over 24h by thin-layer chromatography. IgG integrity was checked by sodium dodecyl sulfate—polyacrylamide gel electrophoresis coupled with Western blot and autoradiography. The radiolabeled Ig’s immunoaffinity was assessed in vitro by a radioimmunoassay method and binding experiments with cells (EL4-hCD20 and EL4-WT). Biodistribution studies were performed in normal BALB/c mice. Tumor uptake was assessed in mice bearing EL4-hCD20 and EL4-WT subcutaneous xenografts. With optimized method, high radiolabeling yields were obtained (95.9 ± 3.5%). 99mTc-IgG-SH was stable in phosphate-buffered saline (4°C and 25°C) and in serum (37°C), even if important sensitivity to transchelation was observed. IgG was not degraded by derivatization and radiolabeling, as shown by Western blot and autoradiography results. 99mTc-anti-CD20 IgG-SH immunoaffinity was estimated with Kd = 35 nM by both methods. In vivo biodistribution studies for 48h showed significant accumulation of radioactivity in plasma, liver, spleen, lungs and kidneys. Planar scintigraphy of mice bearing tumors showed a significant uptake of 99mTc-anti-CD20 IgG-SH in CD20+ tumor versus CD20- tumor. Radiolabeling of derivatized IgG with 99mTc-tricarbonyl was effective, stable and required few antibody amounts. This attractive radiolabeling method is “antibody safe” and preserves Ig affinity for antigen, as shown by both in vitro and in vivo experiments. This method could easily be used with noncommercial IgG or other antibody isotypes.