Inhibition of polyamine biosynthesis preserves β cell function in type 1 diabetes

In preclinical models, α-difluoromethylornithine (DFMO), an ornithine decarboxylase (ODC) inhibitor, delays the onset of type 1 diabetes (T1D) by reducing β cell stress. However, the mechanism of DFMO action and its human tolerability remain unclear. In this study, we show that mice with β cell ODC deletion are protected against toxin-induced diabetes, suggesting a cell-autonomous role of ODC during β cell stress. In a randomized controlled trial (ClinicalTrials.gov: NCT02384889) involving 41 recent-onset T1D subjects (3:1 drug:placebo) over a 3-month treatment period with a 3-month follow-up, DFMO (125-1,000 mg/m2) is shown to meet its primary outcome of safety and tolerability. DFMO dose-dependently reduces urinary putrescine levels and, at higher doses, preserves C-peptide area under the curve without apparent immunomodulation. Transcriptomics and proteomics of DFMO-treated human islets exposed to cytokine stress reveal alterations in mRNA translation, nascent protein transport, and protein secretion. These findings suggest that DFMO may preserve β cell function in T1D through islet cell-autonomous effects.

Responders to low-dose ATG induce CD4+ T cell exhaustion in type 1 diabetes

BACKGROUNDLow-dose anti-thymocyte globulin (ATG) transiently preserves C-peptide and lowers HbA1c in individuals with recent-onset type 1 diabetes (T1D); however, the mechanisms of action and features of the response remain unclear. Here, we characterized the post hoc immunological outcomes of ATG administration and their potential use as biomarkers of metabolic response to therapy (i.e., improved preservation of endogenous insulin production).METHODSWe assessed gene and protein expression, targeted gene methylation, and cytokine concentrations in peripheral blood following treatment with ATG (n = 29), ATG plus granulocyte colony-stimulating factor (ATG/G-CSF, n = 28), or placebo (n = 31).RESULTSTreatment with low-dose ATG preserved regulatory T cells (Tregs), as measured by stable methylation of FOXP3 Treg-specific demethylation region (TSDR) and increased proportions of CD4+FOXP3+ Tregs (P < 0.001) identified by flow cytometry. While treatment effects were consistent across participants, not all maintained C-peptide. Responders exhibited a transient rise in IL-6, IP-10, and TNF-α (P < 0.05 for all) 2 weeks after treatment and a durable CD4+ exhaustion phenotype (increased PD-1+KLRG1+CD57- on CD4+ T cells [P = 0.011] and PD1+CD4+ Temra MFI [P < 0.001] at 12 weeks, following ATG and ATG/G-CSF, respectively). ATG nonresponders displayed higher proportions of senescent T cells (at baseline and after treatment) and increased methylation of EOMES (i.e., less expression of this exhaustion marker).CONCLUSIONAltogether in these exploratory analyses, Th1 inflammation-associated serum and CD4+ exhaustion transcript and cellular phenotyping profiles may be useful for identifying signatures of clinical response to ATG in T1D.TRIAL REGISTRATIONClinicalTrials.gov NCT02215200.FUNDINGThe Leona M. and Harry B. Helmsley Charitable Trust (2019PG-T1D011), the NIH (R01 DK106191 Supplement, K08 DK128628), NIH TrialNet (U01 DK085461), and the NIH NIAID (P01 AI042288).

AB0424 A RANDOMIZED, DOUBLE-BLIND, PLACEBO CONTROLLED STUDY OF THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF ALPN-303, A POTENT DUAL BAFF/APRIL INHIBITOR, IN ADULT HEALTHY VOLUNTEERS

Background

Therapeutic agents targeting the B-cell cytokines BAFF and/or APRIL, including the wild-type (WT) TACI-Fc fusion proteins atacicept and telitacicept, have demonstrated promising clinical potential in rheumatic diseases like systemic lupus erythematosus (SLE) and/or other B-cell-related diseases such as autoantibody-related nephritides. ALPN-303 is an Fc fusion protein of a variant, engineered TACI domain which mediates significantly more potent inhibitory activity in vitro as compared to WT TACI-Fc or BAFF- or APRIL-specific monoclonal antibodies, along with enhanced pharmacokinetic (PK) and immunomodulatory properties in preclinical studies1,2. ALPN-303 may therefore significantly improve clinical outcomes in SLE and other B-cell-related diseases.

Objectives

To evaluate the safety, tolerability, PK, and pharmacodynamics (PD) of ALPN-303 in adult healthy volunteers (HV).

Methods

In this first-in-human study (NCT05034484), adult HVs are enrolled in single ascending dose cohorts of intravenously (IV) or subcutaneously (SC) administered ALPN-303. For each IV cohort, the first 2 subjects are randomized 1:1 to receive ALPN-303 or placebo, followed by the remaining 4 subjects randomized 3:1 to receive ALPN-303 or placebo. For each SC cohort, HVs are randomized 4:2 to receive a single SC dose of ALPN-303 or placebo. All subjects are followed to assess safety and PK of ALPN-303, to measure levels of circulating immunoglobulins (Ig), and to characterize leukocyte populations in peripheral blood by flow cytometry.

Results

ALPN-303 has been well tolerated and overall exhibits dose-dependent PK and expected PD effects on circulating Ig levels. Dose escalation is expected to be completed by the time of the meeting; the presentation will include all available safety, PK, and PD (circulating Ig and B-cell population) data.

Conclusion

In this first-in-human study, ALPN-303 demonstrates acceptable preliminary safety and tolerability, and exhibits expected PD effects on circulating Ig and B-cell populations. These findings support future clinical development of ALPN-303 in patients with SLE or other B-cell-mediated diseases.

References

[1]Dillon SR, Evans LS, Lewis KE, et al. OP0039 ALPN-303, an enhanced, potent dual BAFF/APRIL antagonist engineered by directed evolution for the treatment of systemic lupus erythematosus (SLE) and other B cell related autoimmune diseases. Annals of the Rheumatic Diseases 2021;80:21.

[2]Dillon SR, Evans LS, Lewis KE, et al. ALPN-303, an enhanced, potent dual BAFF/APRIL antagonist engineered by directed evolution for the treatment of systemic lupus erythematosus (SLE) and other B cell-related diseases. Arthritis Rheumatol. 2021; 73 (suppl 10).

Disclosure of Interests

Pille Harrison Employee of: Alpine Immune Sciences Inc, Jason Lickliter Consultant of: ENA Oncology and Amplia. Neither of these were developing drugs for rheumatological diseases., Stacey R. Dillon Employee of: Alpine Immune Sciences Inc, Kristi Manjarrez Employee of: Alpine Immune Sciences Inc, Alina Smith Employee of: Alpine Immune Sciences Inc, Melody Dossey Employee of: Alpine Immune Sciences Inc, Lori Blanchfield Employee of: Alpine Immune Sciences Inc, Allison Chunyk Employee of: Alpine Immune Sciences Inc, Hany Zayed Employee of: Alpine Immune Sciences Inc, Stanford L. Peng Employee of: Alpine Immune Sciences Inc

33 Development of a clinical ex vivo assay for the assessment of therapeutic CD28 costimulatory pathway engagement

Background

Preclinical evidence supports combining checkpoint inhibition (CPI) with T cell costimulatory agonism to improve the breadth and durability of anti-tumor responses relative to CPI alone. Currently, there are a number of therapeutic approaches combining costimulatory receptor agonists (e.g. CD28, 4-1BB, OX40L, etc.) with tumor targeting agents and/or CPI. Identification of a pharmacodynamically-justified therapeutic dose can be challenging because traditional duration of target occupancy does not necessarily correlate with immunological activity in the case of costimulatory molecules, and an ‘always on’ dose risks immune exhaustion. ALPN-202, a variant CD80 vIgD-Fc fusion protein that mediates PD-L1-dependent CD28 costimulation and inhibits the PD-L1 and CTLA-4 checkpoints, is in development for the treatment of multiple advanced malignancies. To assess clinical CD28 agonism in the context of ALPN-202 treatment, we developed a novel, ex vivo whole blood target-dependent costimulation (TDC) assay.

Methods

A TDC assay was developed using clinical samples from NEON-1 (NCT04186637), an ongoing dose escalation and expansion clinical trial of ALPN-202 for patients with advanced malignancies. The assay uses patient blood stimulated with paraformaldehyde-fixed, artificial antigen presenting cells (aAPC) expressing both cell-surface anti-CD3 and PD-L1. Pre-dose and end-of-infusion (EOI) blood was drawn from trial participants and co-cultured for 24 hours with the aAPCs in a pre-made assay plate. Plasma was collected and secreted IL-2 was quantified and used as a measure of PD-L1-dependent CD28 costimulation. Nonlinear regression was used to calculate area under the curve (AUC) for each condition, and sample AUC values were compared to a positive control (pre-dose blood stimulated with a fixed concentration of ALPN-202). Serum concentration of ALPN-202 and CD28 target saturation analyses were conducted concurrently to evaluate the exposure-response relationship.

Results

Using the ex vivo TDC assay, ALPN-202 demonstrated PD-L1-dependent T cell costimulation at all dose levels tested to date in the NEON-1 clinical trial, consistent with preclinical assay development data. Similarly, CD28 target saturation levels on circulating T cells correlated with serum concentration of ALPN-202.

Conclusions

We have developed a novel ex vivo assay to assess induction of PD-L1-dependent CD28 costimulation in a therapeutic setting. This assay has been successfully employed to monitor controlled CD28 costimulation by the CD28 agonist therapeutic candidate ALPN-202, helping to establish a PK/PD relationship that is consistent with preclinical data. More broadly, this type of cell-based, ex vivo TDC assay could be adapted to assess costimulatory receptor engagement, particularly target-dependent costimulation, for other therapeutic agonists in clinical development.

Ethics Approval

This study was approved by WCG IRB’s Human Subjects Review, approval number: 20211877.

Distinct waves of CD8 T cell affinity during demyelinating disease progression

The animal model of Multiple Sclerosis, Experimental Autoimmune Encephalomyelitis (EAE), requires CD4 T cells to induce demyelinating disease. However, CD8 T cells are ever present during EAE and have been hypothesized to have both effector and suppressor functions. To understand autoimmune disease progression, we analyzed the affinity and genetic profile of the CD4 and CD8 T cell response over time. Affinity analysis of CD8 T cells during the autoimmune disease course revealed the greatest affinity for myelin at peak disease (d21-23), whereas affinities were significantly lower at onset (d14) and chronic (d36-38) timepoints. Conversely, affinity analysis of CD4 T cells revealed no significant changes at the same time points. Additionally, CD8 T cells displayed a smaller, 10-fold range in affinity, suggestive of a restricted TCR clonal response. CD4 affinities covered a much wider 10,000-fold range, consisting of low and high affinity clones. To further understand the dynamics of the T cell population during disease, we performed single cell RNA-sequencing. Heterogenous populations of CD4 and CD8 T cells were observed at peak EAE disease, including a genetically distinct population of FoxP3+, CD25+ CD8 T cells which accounted for 3.33% the total CD8 population. These genomic data paired with the known associations between affinity and T cell fate suggest phenotypically and functionally distinct waves of CD8 T cells with limited clonality infiltrate the CNS during EAE progression.

Dual Molecular Mechanisms Govern Escape at Immunodominant HLA A2-Restricted HIV Epitope

Serial accumulation of mutations to fixation in the SLYNTVATL (SL9) immunodominant, HIV p17 Gag-derived, HLA A2-restricted cytotoxic T lymphocyte epitope produce the SLFNTIAVL triple mutant “ultimate” escape variant. These mutations in solvent-exposed residues are believed to interfere with TCR recognition, although confirmation has awaited structural verification. Here, we solved a TCR co-complex structure with SL9 and the triple escape mutant to determine the mechanism of immune escape in this eminent system. We show that, in contrast to prevailing hypotheses, the main TCR contact residue is 4N and the dominant mechanism of escape is not via lack of TCR engagement. Instead, mutation of solvent-exposed residues in the peptide destabilise the peptide–HLA and reduce peptide density at the cell surface. These results highlight the extraordinary lengths that HIV employs to evade detection by high-affinity TCRs with a broad peptide-binding footprint and necessitate re-evaluation of this exemplar model of HIV TCR escape.

NFM Cross-Reactivity to MOG Does Not Expand a Critical Threshold Level of High-Affinity T Cells Necessary for Onset of Demyelinating Disease

Of interest to the etiology of demyelinating autoimmune disease is the potential to aberrantly activate CD4⁺ T cells due to cross-recognition of multiple self-epitopes such as has been suggested for myelin oligodendrocyte glycoprotein epitope 35-55 (MOG_35-55) and neurofilament medium protein epitope 15-35 (NFM_15-35). NFM_15-35 is immunogenic in C57BL/6 mice but fails to induce demyelinating disease by polyclonal T cells despite having the same TCR contact residues as MOG_35-55, a known encephalitogenic Ag. Despite reported cross-reactivity with MOG-specific T cells, the polyclonal response to NFM_15-35 did not expand threshold numbers of MOG_38-49 tetramer-positive T cells. Furthermore, NFM lacked functional synergy with MOG to promote experimental autoimmune encephalomyelitis because NFM-deficient synonymous with knockout mice developed an identical disease course to wild-type mice after challenge with MOG_35-55 Single-cell analysis of encephalitogenic T cells using the peptide:MHC monomer-based two-dimensional micropipette adhesion frequency assay confirmed that NFM was not a critical Ag driving demyelinating disease because NFM_18-30-specific T cells in the CNS were predominantly reactive to MOG_38-49 The absence of NFM contribution to disease allowed mapping of the amino acids required for encephalitogenicity and expansion of high-affinity, MOG-specific T cells that defined the polyclonal response. Alterations of N-terminal residues outside of the NFM_15-35 core nonamer promoted expansion of high-affinity, MOG_38-49 tetramer-positive T cells and promoted consistent experimental autoimmune encephalomyelitis induction, unlike mice challenged with NFM_15-35 Although NFM_15-35 is immunogenic and cross-reactive with MOG at the polyclonal level, it fails to expand a threshold level of encephalitogenic, high-affinity MOG-specific T cells.

Ratiometric Tension Probes for Mapping Receptor Forces and Clustering at Intermembrane Junctions

Short-range communication between cells is required for the survival of multicellular organisms. One mechanism of chemical signaling between adjacent cells employs surface displayed ligands and receptors that only bind when two cells make physical contact. Ligand-receptor complexes that form at the cell-cell junction and physically bridge two cells likely experience mechanical forces. A fundamental challenge in this area pertains to mapping the mechanical forces experienced by ligand-receptor complexes within such a fluid intermembrane junction. Herein, we describe the development of ratiometric tension probes for direct imaging of receptor tension, clustering, and lateral transport within a model cell-cell junction. These probes employ two fluorescent reporters that quantify both the ligand density and the ligand tension and thus generate a tension signal independent of clustering. As a proof-of-concept, we applied the ratiometric tension probes to map the forces experienced by the T-cell receptor (TCR) during activation and showed the first direct evidence that the TCR-ligand complex experiences sustained pN forces within a fluid membrane junction. We envision that the ratiometric tension probes will be broadly useful for investigating mechanotransduction in juxtacrine signaling pathways.

Tissue-specific antigens induce dual complementary T cell tolerance mechanisms

To understand tolerance mechanisms to tissue-specific antigens, we probed the development of polyclonal T cells specific for myelin oligodendrocyte glycoprotein (MOG), a myelin antigen targeted during autoimmune demyelinating disease. We find T cell tolerance occurs via two thymocyte selection processes. First, the presence of tissue-specific antigen intrinsically broadens the TCR repertoire to lower overall reactivity of effector T cells. Second, expression of MOG extrinsically induces a higher frequency of more efficacious antigen-specific Foxp3+ regulatory T cell population that prevents autoimmunity. Interestingly, clonal deletion mediated by thymocyte negative selection of high-affinity T cells was not apparent. Thus, cooperative tolerance exists to prevent autoimmunity towards tissue-specific antigens.

TCR affinity and tolerance mechanisms converge to shape T cell diabetogenic potential

Autoreactive T cells infiltrating the target organ can possess a broad TCR affinity range. However, the extent to which such biophysical parameters contribute to T cell pathogenic potential remains unclear. In this study, we selected eight InsB9-23-specific TCRs cloned from CD4(+) islet-infiltrating T cells that possessed a relatively broad range of TCR affinity to generate NOD TCR retrogenic mice. These TCRs exhibited a range of two-dimensional affinities (∼ 10(-4)-10(-3) μm(4)) that correlated with functional readouts and responsiveness to activation in vivo. Surprisingly, both higher and lower affinity TCRs could mediate potent insulitis and autoimmune diabetes, suggesting that TCR affinity does not exclusively dictate or correlate with diabetogenic potential. Both central and peripheral tolerance mechanisms selectively impinge on the diabetogenic potential of high-affinity TCRs, mitigating their pathogenicity. Thus, TCR affinity and multiple tolerance mechanisms converge to shape and broaden the diabetogenic T cell repertoire, potentially complicating efforts to induce broad, long-term tolerance.

Cytokine-neuroantigen fusion proteins represent a novel therapeutic approach for EAE (48.10)

Cytokine-neuroantigen (NAg) fusion proteins have promise as a new class of antigen-specific therapies for treatment of CNS autoimmune disease. The primary objective of this study was to assess therapeutic efficacy of selected cytokine-neuroantigen fusion proteins in the Lewis rat model of EAE. The neuroantigen domain of each fusion protein was comprised of the major encephalitogenic determinant of myelin basic protein. Three cytokine-NAg fusion proteins were potent inhibitors of EAE. These fusion proteins incorporated the IL-2 cytokine as the N-terminal domain (the IL2NAg fusion protein), the secreted IL-16 cytokine as the C-terminal domain (the NAgIL16 fusion protein), or the IFN-beta cytokine as the N-terminal domain (IFNbeta-NAg fusion protein). Compared to NAg alone, these fusion proteins strongly attenuated the subsequent active induction of EAE. These fusion proteins also inhibited EAE when administered after encephalitogenic challenge during onset of EAE. In conclusion, cytokine-NAg fusion proteins that incorporate IL-2, IL-16, or IFN-beta cytokine domains may comprise an effective tolerogenic therapy for CNS autoimmune disease.