Abstract OT2-10-01: A phase 2, randomized study of magrolimab combination therapy in adult patients with unresectable locally advanced or metastatic triple-negative breast cancer

Background: Improving outcomes for patients (pts) with triple-negative breast cancer (TNBC) remains a high unmet need. Immune checkpoint inhibitors (ICIs) + chemotherapy (chemo) and single-agent sacituzumab govitecan, a trophoblast cell-surface antigen 2–targeted antibody-drug conjugate coupled to SN38 via a proprietary, hydrolysable linker, are approved in newly diagnosed pts with programmed death-ligand 1 (PD-L1)–positive tumors and pts who received ≥2 prior systemic therapies (≥1 for metastatic disease), respectively. However, additional options are urgently needed, particularly for pts with tumors that do not express PD-L1 and for those with progression on chemo ± ICI. Magrolimab is an antibody blocking CD47, a “don’t eat me” signal overexpressed on cancer cells, including TNBC, inducing tumor phagocytosis by macrophages. Magrolimab has shown preclinical activity and promising clinical efficacy in hematologic and solid tumors. Chemo agents, including taxanes, can enhance prophagocytic signals on tumor cells, leading to the potential for synergistic antitumor activity with magrolimab. This study is evaluating the safety/tolerability and efficacy of magrolimab in combination with nab-paclitaxel/paclitaxel or with sacituzumab govitecan in unresectable locally advanced/metastatic TNBC. Trial Design: This open-label, 2-cohort (C) study consists of safety run-in and phase (ph)2 portions evaluating nab-paclitaxel/paclitaxel (choice) + magrolimab (safety run-in) or ± magrolimab (ph2, randomized 1:1) in pts with untreated, advanced/metastatic TNBC ineligible for ICI (C1) and magrolimab + sacituzumab govitecan (safety run-in and ph2) in pts with advanced TNBC who received 1 prior systemic treatment in the metastatic setting (C2). Stratification factors for C1 are neoadjuvant and/or adjuvant taxane therapy, liver metastases, and nab-paclitaxel vs paclitaxel. In both cohorts, magrolimab will be administered intravenously (IV) in de-escalating doses to establish the recommended ph2 dose (RP2D). Nab-paclitaxel/paclitaxel and sacituzumab govitecan will be administered IV per standard of care. Eligibility Criteria: Eligible pts are ≥18 y with PD-L1–negative, untreated, unresectable locally advanced/metastatic TNBC (C1) or unresectable locally advanced/metastatic TNBC who received 1 prior line of therapy in the advanced setting, including a taxane and an ICI if PD-L1 positive (C2), with measurable disease per RECIST v1.1. Exclusion criteria include active central nervous system disease, red blood cell transfusion dependence, or prior treatment with CD47/signal regulatory protein α–targeting agents for both cohorts. Additional exclusions are disease progression within 6 months of (neo)adjuvant therapy or rapid visceral progression and/or symptomatic disease, for which single-agent chemo would not be appropriate (C1); chronic inflammatory bowel disease and a history of bowel obstruction or gastrointestinal perforation within 6 months of enrollment, prior treatment with topoisomerase I inhibitors or antibody-drug conjugates containing a topoisomerase inhibitor, and receipt of high-dose systemic corticosteroids within 2 weeks of cycle 1 day 1 (C2). Specific Aims: The primary objectives are safety/tolerability and magrolimab RP2D (safety run-in) and efficacy (ph2: C1, progression-free survival [PFS]; C2, objective response rate [ORR]; both by investigator). Secondary objectives include ORR, PFS, and duration of response by investigator and independent central review, overall survival, and magrolimab concentration vs time and antidrug antibodies. Present and Target Accrual: The study is enrolling in the US, Australia, and Hong Kong. Target accrual is 144 pts. Contact Information: ClinicalTrials.gov: NCT04958785.

Citation Format: Natalie Rainey, Rohit Joshi, Joanne Win Yang Chiu, Ann Chen, Hao Wang, Jared Odegard, Michael Howland, Sylvia Adams. A phase 2, randomized study of magrolimab combination therapy in adult patients with unresectable locally advanced or metastatic 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 OT2-10-01.

Identical and Nonidentical Twins: Risk and Factors Involved in Development of Islet Autoimmunity and Type 1 Diabetes

OBJECTIVE

There are variable reports of risk of concordance for progression to islet autoantibodies and type 1 diabetes in identical twins after one twin is diagnosed. We examined development of positive autoantibodies and type 1 diabetes and the effects of genetic factors and common environment on autoantibody positivity in identical twins, nonidentical twins, and full siblings.

RESEARCH DESIGN AND METHODS

Subjects from the TrialNet Pathway to Prevention Study (N = 48,026) were screened from 2004 to 2015 for islet autoantibodies (GAD antibody [GADA], insulinoma-associated antigen 2 [IA-2A], and autoantibodies against insulin [IAA]). Of these subjects, 17,226 (157 identical twins, 283 nonidentical twins, and 16,786 full siblings) were followed for autoantibody positivity or type 1 diabetes for a median of 2.1 years.

RESULTS

At screening, identical twins were more likely to have positive GADA, IA-2A, and IAA than nonidentical twins or full siblings (all P < 0.0001). Younger age, male sex, and genetic factors were significant factors for expression of IA-2A, IAA, one or more positive autoantibodies, and two or more positive autoantibodies (all P ≤ 0.03). Initially autoantibody-positive identical twins had a 69% risk of diabetes by 3 years compared with 1.5% for initially autoantibody-negative identical twins. In nonidentical twins, type 1 diabetes risk by 3 years was 72% for initially multiple autoantibody-positive, 13% for single autoantibody-positive, and 0% for initially autoantibody-negative nonidentical twins. Full siblings had a 3-year type 1 diabetes risk of 47% for multiple autoantibody-positive, 12% for single autoantibody-positive, and 0.5% for initially autoantibody-negative subjects.

CONCLUSIONS

Risk of type 1 diabetes at 3 years is high for initially multiple and single autoantibody-positive identical twins and multiple autoantibody-positive nonidentical twins. Genetic predisposition, age, and male sex are significant risk factors for development of positive autoantibodies in twins.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Loss of tolerance due to post-translational modification of beta cell peptides (BA11P.124)

Post-translational modification (PTM) of self-proteins generates neo-antigens that are clinically relevant to autoimmune disease and are increasingly implicated in T1D. Here we demonstrate that enzymatic transglutamination and citrullination of beta cell antigens enhances presentation by the high risk HLA class II alleles DR4 and DQ8. We show CD4+ T cells specific for these epitopes are present at elevated frequencies ex vivo in the peripheral blood of patients with long standing T1D and are of Th1 phenotype. Such neo-antigens can induce distinct T cell specificities, while others cross-react with wild type-specific T cells. In each case, autoreactive T cells preferentially recognize modified epitopes resulting in enhanced proliferation and cytokine production. Mechanistically, modification at key binding pockets enhanced peptide binding to HLA class II, creating a stable pMHC that could bind autoreactive CD4+ T cells. Alternatively, modification of residues outside of binding pockets altered TCR interaction to permit T cell recognition. In one instance, dual modification of HLA and TCR contact points was required to induce a T cell response. Interrogation of autoantibody positive, healthy “non-progressors” revealed an intermediate T cell frequency, representing a break in tolerance without progression to overt diabetes. These findings implicate an important role for PTMs in broadening the antigenic repertoire and exacerbating the evolving autoimmune response in T1D.

Recognition of posttranslationally modified GAD65 epitopes in subjects with type 1 diabetes

Posttranslational modification (PTM) of self-proteins has been shown to elicit clinically relevant immune responses in rheumatoid arthritis and celiac disease. Accumulating evidence suggests that recognition of modified self-proteins may also be important in type 1 diabetes. Our objective was to identify posttranslationally modified GAD65 peptides, which are recognized by subjects with type 1 diabetes, and to assess their disease relevance. We show that citrullination and transglutamination of peptides can enhance their binding to DRB1*04:01, a diabetes-susceptible HLA allele. These and corresponding modifications to amino acids at T-cell contact positions modulated the recognition of multiple GAD65 peptides by self-reactive T cells. Using class II tetramers, we verified that memory T cells specific for these modified epitopes were detectable directly ex vivo in the peripheral blood of subjects with type 1 diabetes at significantly higher frequencies than healthy controls. Furthermore, T cells that recognize these modified epitopes were either less responsive or nonresponsive to their unmodified counterparts. Our findings suggest that PTM contributes to the progression of autoimmune diabetes by eliciting T-cell responses to new epitope specificities that are present primarily in the periphery, thereby circumventing tolerance mechanisms.

Bcl6 is required for the development of T follicular helper cells marked by downregulation of P-selectin glycoprotein ligand-1 (46.7)

Follicular helper T cells (TFH), defined by expression of the surface markers CXCR5, PD-1 and ICOS, are located in germinal centers where they provide help for B cell maturation through the secretion of IL-21. The transcriptional repressor Bcl6 is upregulated in TFH cells; however, the role that it plays in their development is unknown. We describe downregulation of P-selectin glycoprotein ligand-1 (PSGL1) as a new surface marker for TFH cells, and show that Bcl6 is required for the development of TFH cells that are PSGL1lo. Activated antigen-specific CD4 PSGL1lo T cells are enriched for expression of CXCR5 and PD-1, and highly upregulate IL-21 and Bcl6. Over-expression of Bcl6 leads to an increase in PSGL1lo TFH cells; however, it cannot rescue TFH cell development in the absence of ICOS. Consistent with others, we find B cells are required for full development of TFH cells, but not for downregulation of PSGL1, suggesting there are multiple steps in development of the subset. This data demonstrates that Bcl6, independent of ICOS signaling, is critical for the development of this lineage.

Analysis of inbreeding depression in the first litter size of mice in a long-term selection experiment with respect to the age of the inbreeding

An understanding of inbreeding and inbreeding depression are important in evolutionary biology, conservation genetics, and animal breeding. A new method was developed to detect departures from the classical model of inbreeding; in particular, it investigated differences between the effects of inbreeding in recent generations from that in the more distant past. The method was applied in a long-term selection experiment on first-litter size in mice. The total pedigree included 74,630 animals with approximately 30,000 phenotypic records. The experiment comprised several different lines. The highest inbreeding coefficients (F) within a line ranged from 0.22 to 0.64, and the average effective population size (N(e)) was 58.1. The analysis divided F into two parts, corresponding to the inbreeding occurring in recent generations ('new') and that which preceded it ('old'). The analysis was repeated for different definitions of 'old' and 'new', depending on length of the 'new' period. In 15 of these tests, 'new' inbreeding was estimated to cause greater depression than 'old'. The estimated depression ranged from -11.53 to -0.79 for the 'new' inbreeding and from -5.22 to 15.51 for 'old'. The difference was significant, the 'new' period included at least 25 generations of inbreeding. Since there were only small differences in N(e) between lines, and near constant N(e) within lines, the effect of 'new' and 'old' cannot be attributed to the effects of 'fast' versus 'slow' inbreeding. It was concluded that this departure from the classical model, which predicts no distinction between this 'old and 'new' inbreeding, must implicate natural selection and purging in influencing the magnitude of depression.

Abrogation of skin disease in LUPUS-prone MRL/FASlpr mice by means of a novel tylophorine analog

OBJECTIVE

To test the therapeutic effect of DCB-3503, a synthetic compound derived from a natural product that inhibits NF-kappaB, on end-organ disease in the MRL-Fas(lpr) murine model of systemic lupus erythematosus (SLE).

METHODS

Eight-week-old female MRL/Fas(lpr) mice were treated intraperitoneally with a low (2 mg/kg) or high (6 mg/kg) dose of DCB-3503 for 10 weeks. Control groups were administered vehicle treatment alone (negative control) or 25 mg/kg cyclophosphamide (positive control). Mice were bled before (8 weeks) and during (13 weeks) treatment, and when they were killed (20 weeks), and serum samples were analyzed for total IgM and IgG levels and autoantibody titers. When the mice were killed, spleen and lymph nodes (axillary, brachial, and cervical) were examined by flow cytometric analysis. The presence of skin and renal disease was determined by histopathologic analysis.

RESULTS

DCB-3503 reduced anti-double-stranded DNA and antichromatin autoantibodies and nearly abrogated inflammatory skin disease in MRL/Fas(lpr) mice; however, it had little effect on histologic kidney disease. Treated mice did not have hematologic or hepatic toxicity. These data indicate that end-organ disease in MRL/Fas(lpr) mice responds differentially to NF-kappaB inhibitor.

CONCLUSION

DCB-3503 causes significant abrogation of skin disease in MRL/Fas(lpr) mice and may potentially be beneficial in the treatment of inflammatory skin disease in SLE.