Abstract OT1-03-01: XMT-1660: A Phase 1b trial of a B7-H4 targeted Antibody Drug Conjugate (ADC) in Breast, Endometrial, and Ovarian Cancers

Background: Breast cancer (BC) is the most commonly diagnosed cancer and one of the leading causes of cancer death in women. Despite significant therapeutic advances, the majority of patients with unresectable or recurrent/metastatic disease eventually develop resistance to available standard of care (SOC) therapies. B7-H4 is a poor prognostic factor and is overexpressed in several cancers including endometrial, ovarian, and breast. As a member of the CD28/B7 family of cell surface proteins, it promotes tumorigenesis by suppressing anti-tumor immunity. XMT-1660 is a B7-H4-targeted Dolasynthen antibody drug conjugate with a precise, optimized drug-to-antibody ratio and a DolaLock microtubule inhibitor payload with controlled bystander effect. In the preclinical setting, XMT-1660 has demonstrated anti-tumor activity in TNBC and ER+/HER2- patient-derived xenograft mouse models, which included tumors from heavily pre-treated patients (Collins et al, AACR 2022). Increased anti-tumor activity tended to be more frequent in models with higher B7-H4 expression, providing rationale for a Ph1 clinical trial. Methods: The Ph1 trial includes a first-in-human open-label dose escalation (DES) portion followed by dose expansion (EXP) evaluating XMT-1660 in patients with BC, EC, and OC following progression on SOC as applicable (i.e., CDK4/6i + ET; platinum-based chemotherapy). In the DES, Bayesian Optimal Interval (BOIN) design will be used to determine the MTD. Patients will receive XMT-1660 IV Q3 weeks. Primary endpoints in DES are to assess safety and determine a recommended phase 2 dose (RP2D) and assessment of preliminary efficacy as a secondary endpoint. In the EXP portion, cohorts enrolling TNBC, ER+/HER2- BC, EC/OC are planned and additional patients may be enrolled based on emerging data. The primary endpoint of EXP is to assess safety and tolerability, overall response rate, disease control rate, and duration of response. Secondary endpoints include pharmacokinetic analysis and antidrug antibodies. Patients are not selected by B7-H4 status, but baseline tumors samples are collected for retrospective tumor tissue evaluation. The trial is currently enrolling patients. NCT05377996

Citation Format: Erika Hamilton, Arvind Chaudhry, Alexander I. Spira, Sylvia Adams, Nour Abuhadra, Antonio Giordano, Ritesh Parajuli, Hyo S. Han, Amy Weise, Aubri Marchesani, Kate Josephs, Chu Ri Shin, Kevin Kalinsky. XMT-1660: A Phase 1b trial of a B7-H4 targeted Antibody Drug Conjugate (ADC) in Breast, Endometrial, and Ovarian Cancers [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 OT1-03-01.

First-in-human data of ALLO-501A, an allogeneic chimeric antigen receptor (CAR) T-cell therapy and ALLO-647 in relapsed/refractory large B-cell lymphoma (R/R LBCL): ALPHA2 study

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Background: Allogeneic CAR T cell therapy addresses logistical/manufacturing challenges inherent in autologous (auto) CAR T therapy. ALLO-501A, which uses Cellectis technologies, is an allogeneic anti-CD19 CAR T cell product whose a) disrupted TCRα gene may reduce GvHD risk, and b) edited CD52 gene may permit use of ALLO-647 (a humanized anti-CD52 mAb) to selectively deplete host T cells. Methods: The ongoing ALPHA2 study is a single-arm, open-label, 2 phase study of ALLO-501A in non-HLA matched patients (pts) with R/R LBCL and ≥2 prior lines of therapy. Prior auto CD19 CAR T therapy is allowed if tumors remain CD19+. Following lymphodepletion (LD) with ALLO-647 (60 mg or 90 mg), fludarabine 30 mg/m2/d x 3d (Flu), and cyclophosphamide 300 mg/m2/d x 3d (Cy), escalating doses of ALLO-501A (40 [DL1] or 120 [DL2] x 106 viable CAR T cells) were administered. Retreatment was allowed for PD or SD with suboptimal CAR T expansion. Pts who had ≥SD at D28 could receive a second dose in a consolidation cohort. Phase 1 assessed safety/tolerability and cell kinetics of escalating doses of ALLO-501A following LD. Results: By 1/15/21, 11/11 enrolled pts received ALLO-647 (60 mg: n=6; 90 mg: n=5). Mean duration from enrollment to start of therapy was 6 days. After LD, 1 and 9 pt(s) were treated with ALLO-501A at DL1 and DL2, respectively; 1 pt developed CNS lymphoma and was not treated. Of 10 pts treated, 1 pt received retreatment and 4 pts were enrolled in the consolidation cohort. Pts had a median age of 60 years; 8 were ≥ stage III at diagnosis, 5 had IPI scores ≥3, and 3 had baseline LDH > 2x ULN. Median number of prior therapies was 3 (range 2 – 7); 3 pts had received auto CD19 CAR T cell therapy. 4/8 evaluable pts had rapidly PD at study entry. Median FU was 1.7 months. No dose modifications were required and no pt experienced DLTs. The most common AEs were anemia, leukopenia, neutropenia and thrombocytopenia (73%); and lymphopenia (64%). No GvHD or ICANS were reported. CRS was seen in 2 (18%) pts, both Grade < 3. Infusion-related reactions, all grade <3, were observed in 4 (36%) pts. D28 response data are available for 8 pts: 1 died of PD before D28; 4 additional pts had PD, including 2 who progressed 2 and 3 mos. after auto CAR T; 1 had SD; and 2 (both DL2) had CR. Of those in CR, 1 had peak ALLO-501A expansion at D14, persistence until D42, and ongoing CR at 4 mo; 1, with a 4-mo response to prior auto CAR T, had peak expansion at D28 and remains in ongoing CR at D56 after ALLO-501A with pending persistence. Conclusions: This dose escalation cohort contained heavily pretreated, actively progressing pts, some of whom had failed auto CAR T. Preliminary data suggest an acceptable safety profile following ALLO-501A and ALLO-647 and early signs of efficacy in LBCL. Enrollment into the consolidation cohort is ongoing; updated clinical/biomarker data of resistance and clinical activity will be presented. Clinical trial information: NCT04416984.

Anti-PD-1 antibody cetrelimab (JNJ-63723283) in patients with advanced cancers: Updated phase I/II study results

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Background: Cetrelimab (JNJ-63723283) is an IgG4, anti-programmed cell death protein-1 (PD-1) antibody. Here we present updated results from an ongoing phase 1/2 study of cetrelimab in patients (pts) with advanced or refractory solid cancers. Methods: Part 2 of the study evaluated safety and efficacy of cetrelimab at 240 mg Q2W, a recommended phase 2 dose selected in Part 1 (Calvo JCO 2018; 36 suppl 5:58). Tumor types for Part 2 included non-small cell lung cancer (NSCLC), melanoma (MEL), bladder, renal cell, small cell lung cancer (SCLC), microsatellite-high (MSI-H)/DNA mismatch repair deficient (dMMR; locally or centrally tested) colorectal cancer (CRC) and gastric/esophageal cancer (GCA/EC). Tumor response was assessed by the investigator following RECIST v1.1. Results: As of 3 Sep 2018, 192 pts have been treated with cetrelimab from 80–800 mg Q2W and 480 mg Q4W. Median age was 60 years (23–86), and median prior regimens was 2 (1–12). Median duration of treatment was 85 days (1–561); 82 pts remain on treatment. Full receptor occupancy was maintained throughout dosing interval. Most common adverse events (AEs) were asthenia (19%), fatigue (19%), dyspnea (16%) and diarrhea (16%). Grade ≥3 AEs, regardless of causality, were reported in 45% of pts; most common were anemia (6%), dyspnea (4%), increased ALT (3%) and increased AST (3%). Observed serious AEs were dyspnea (4%), pleural effusion and intestinal obstruction (3% each). All grade and grade ≥3 immune-related AEs were reported in 30% and 7% of pts, respectively. Among response-evaluable pts (n = 156) from Parts 1 and 2, overall response rate (ORR) was 15%, with 2 complete and 22 partial responses. Half of pts had stable disease or better. ORR was 26% (7/27) in NSCLC (42% [5/12] in PD-L1+ NSCLC [≥50% by IHC]), 25% (12/49) in MEL (28% [12/43] in non-uveal MEL), 50% (1/2) in renal cancer, 8% (2/26) in MSI-H/dMMR CRC (recruited later per amendment) and 14% (2/14) in GCA/EC. No responses were observed in bladder cancer (n = 4) or SCLC (n = 10). Conclusions: The safety profile and preliminary activity of cetrelimab in immune-sensitive advanced cancers is consistent with known PD-1 inhibitors. The study is ongoing and analysis by PD-L1 status will be reported later. Clinical trial information: NCT02908906.

Infliximab Is Not Associated With Increased Risk of Malignancy or Hemophagocytic Lymphohistiocytosis in Pediatric Patients With Inflammatory Bowel Disease

BACKGROUND AND AIMS

Immunosuppressive therapy for inflammatory bowel disease (IBD) in pediatric patients is thought to increase the risk of malignancy and lymphoproliferative disorders, including hemophagocytic lymphohistiocytosis (HLH). We compared unadjusted incidence rates of malignancy and HLH in pediatric patients with IBD exposed to infliximab (IFX) with patients not exposed to biologics and calculated standardized incidence ratios (SIRs).

METHODS

We collected and analyzed data from 5766 participants in a prospective study of long-term outcomes of pediatric patients with IBD (NCT00606346), from May 31, 2007 through June 30, 2016. Patients were 17 years old or younger and had Crohn's disease, ulcerative colitis, or IBD-unclassified with 24,543.0 patient-years of follow-up. We estimated incidence rates for malignancy and HLH as events/1000 patient-years of follow-up. We calculated age-, sex-, and race-adjusted SIRs, with 95% confidence intervals (CIs), using the Surveillance, Epidemiology, and End Results Program (SEER) database.

RESULTS

Thirteen of the 15 patients who developed a malignancy and all 5 of the patients who developed HLH had been exposed to thiopurines; 10 patients with malignancy had also been exposed to a biologic agent. Unadjusted incidence rates showed no increased risk of malignancy (0.46/1000 patient-years) or HLH (0.0/1000 patient-years) in patients exposed to IFX as the only biologic vs those unexposed to biologics (malignancy: 1.12/1000 patient-years; HLH: 0.56/1000 patient-years). SIRs did not demonstrate an increased risk of malignancy among patients exposed to IFX (SIR, 1.69; 95% CI, 0.46-4.32) vs patients not exposed to a biologic agent (SIR, 2.17; 95% CI, 0.59-5.56), even when patients were stratified by thiopurine exposure.

CONCLUSIONS

In determination of age-, sex-, and race-adjusted SIRs using data from a large clinical study and the SEER database, we found that IFX exposure did not associate with increased risk of malignancy or HLH in pediatric patients with IBD. Thiopurine exposure is an important precedent event for the development of malignancy or HLH in pediatric patients with IBD.

Safety and efficacy of trabectedin when administered in the inpatient vs. outpatient setting in a subset analysis of a phase III randomized clinical trial

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Background: Trabectedin (T) has been shown to improve progression free survival (PFS) (4.2 vs 1.5 months, HR 0.55, p < 0.0001) in comparison to dacarbazine (D) in patients (pts) with advanced leiomyosarcoma or liposarcoma following failure of prior chemotherapy. Pts randomized to T in this phase III trial (ET743-SAR 3007) received T as a 24 hr IV infusion in either an inpatient (InP) or outpatient (OP) setting, based upon site preference. Here we report the safety, efficacy, and patient reported outcomes (PROs) of pts based on first infusion site of care. Methods: Pts were randomized 2:1 to receive T (1.5 mg/m2) or D (1 g/m2 over 20-120 min). Site of T infusion was based on institutional preference/standard of care. The site of T administration (InP vs OP) was collected for the first infusion with the assumption that site of care was unchanged for subsequent doses. Results: Of 378 pts treated with T, 100 (27%) and 277 (73%) pts received T as InP or OP, respectively. No differences were observed in PFS or overall survival (OS) by site of care (InP vs OP): Median PFS of 4.1 vs 4.2 months; HR 0.90, p = 0.49 and median OS of 14.3 vs 13.7 months; HR 0.89, p = 0.40. No difference in other efficacy endpoints between InP vs OP were observed: disease control rate (CR+PR+(SD≥18wks)) (38% vs 33%; Odds Ratio [OR] 1.22; p = 0.44) and Overall Response Rate (14% vs 8%; OR 1.76; p = 0.15)). Grade 3-4 adverse events (AEs) occurred in 87% InP vs 79% OP pts and grade 3-4 SAEs occurred in 43% InP vs 33% OP. The most common grade 3-4 AEs in both groups were increased ALT/AST, hematologic toxicity, nausea and fatigue. The incidence of grade 3-4 febrile neutropenia was similar in both groups at 5.0% InP vs 4.7% OP, as was increased blood creatine phosphokinase at 5.0% InP vs 6.1% OP, and catheter related complications of any grade at 16% InP vs 15% OP. No clinically meaningful differences were observed in PROs measured by MD Anderson Symptom Inventory scores. Conclusions: The majority of patients randomized to the trabectedin arm of the ET743-SAR-3007 Phase III study received trabectedin in the OP setting. Treatment outcomes with trabectedin suggest equivalent efficacy and safety when administered in the InP or OP setting. Clinical trial information: NCT01343277.

Incidence of acute and chronic graft-versus-host disease and donor T-cell chimerism after small bowel or combined organ transplantation

PURPOSE

Graft-versus-host disease (GVHD) after organ transplantation is a rare but life-threatening complication with very high mortality.

METHODS

A retrospective review was performed of all patients undergoing small bowel or combined organ transplantation at a single institution during 2003 to 2009. Patients with donor T-cell chimerism were analyzed in detail for development of GVHD.

RESULTS

Thirty-two patients were included in the study. Of 32 patients, 11 (34%) had donor T-cell chimerism (range, 0%-53%) studies performed; 7 (64%) of those 11 patients demonstrated clinical features of GVHD. All patients who demonstrated GVHD had detectable donor T-cell chimerism. All patients with GVHD presented with skin involvement. Graft-versus-host disease responded to increased immune suppression therapy. Mortality was 43% (3/7) among patients with GVHD and was caused by multiorgan failure and sepsis in all cases.

CONCLUSION

Acute and chronic GVHD were observed frequently after combined solid organ transplantation and were associated with significant mortality and morbidity. Alloreactive donor T cells cotransplanted with the organ likely play a role in the pathophysiology because levels of donor-derived T-cell chimerism correlated with the clinical course of GVHD.

Differential platelet-activating factor synthesis by monocytes and polymorphonuclear leukocytes from subjects with localized aggressive periodontitis

BACKGROUND AND OBJECTIVE

Platelet-activating factor is elevated in localized aggressive periodontitis. We previously demonstrated that the elevated level of platelet-activating factor in localized aggressive periodontitis is at least partially attributable to low levels of platelet-activating factor acetylhydrolase, the enzyme that catabolizes platelet-activating factor. The objective of this study was to determine if platelet-activating factor synthesis was also elevated in localized aggressive periodontitis. To test this, platelet-activating factor synthesis was quantified in the monocytes and polymorphonuclear neutrophils of periodontally healthy patients and of subjects with localized aggressive periodontitis.

MATERIAL AND METHODS

Cells were labeled with [(3)H]acetate and treated with vehicle or stimulated with calcium ionophore A23187. Platelet-activating factor was extracted and quantified by scintillation counting.

RESULTS

For both subject groups, resting monocytes and polymorphonuclear neutrophils produced platelet-activating factor, and calcium ionophore A23187 stimulated platelet-activating factor production in both cell types. However, calcium ionophore A23187-activated monocytes from subjects with localized aggressive periodontitis produced less platelet-activating factor than did activated periodontally healthy monocytes (p < 0.0001), suggesting an aberrant calcium ionophore A23187 response in monocytes from subjects with localized aggressive periodontitis. Indeed, when the data were expressed as fold induction of platelet-activating factor synthesis in response to calcium ionophore A23187, monocytes from subjects with localized aggressive periodontitis exhibited only a fourfold increase in platelet-activating factor synthesis, whereas calcium ionophore A23187-stimulated monocytes from periodontally healthy, chronic periodontitis and generalized aggressive periodontitis subjects produced approximately 12 times more platelet-activating factor than did resting monocytes. In contrast, both resting and activated localized aggressive periodontitis polymorphonuclear neutrophils synthesized more platelet-activating factor than did periodontally healthy polymorphonuclear neutrophils.

CONCLUSION

These data suggest that high levels of platelet-activating factor in subjects with localized aggressive periodontitis result from both increased synthesis and reduced catabolism. While localized aggressive periodontitis polymorphonuclear neutrophils contribute to increased platelet-activating factor mass through synthesis, the contribution of monocytes is probably the result of reduced catabolism by platelet-activating factor acetylhydrolase.