Potent Pyrrolobenzodiazepine Research Articles

Abstract C098: Targeting high-expression LGR5 by an R-spondin-based peptibody-drug conjugate is efficacious against neuroblastoma

Abstract Neuroblastoma (NB) is a pediatric tumor that predominantly affects infants and young children, with high-risk (HR) disease being diagnosed in approximately 50% of patients at 18 months or older. LGR4-6 are membrane receptors that bind RSPO ligands, activating Wnt signaling. LGR5, specifically expressed in adult stem cells, is highly upregulated in gastrointestinal (GI) cancers. In NB, high LGR5 expression is associated with aggressive disease and poor outcomes. Knockdown of LGR5 reduces cell growth in LGR5-high NB cell lines. The R-spondin-LGR5 axis has emerged as a potential therapeutic target due to its involvement in stem cell proliferation and self-renewal, as well as its overexpression in certain cancers, including neuroblastoma. RSPO-based peptibody drug conjugate (PDC) is a promising approach to target LGR4/5 for HR-NB therapy. PDCs are designed to selectively deliver the potent Pyrrolobenzodiazepine (PBD) dimer SG3199 to LGR5 high-expressing neuroblastoma cells using a peptibody that mimics the R-spondin binding activity of LGR5 ligands. Our preclinical study showed the efficacy of DAR2 R-spondin-based PDCs, generated through microbial transglutaminase-mediated site-specific conjugation, inducing cell death both in vitro and in vivo. Furthermore, these PDCs demonstrate reduced tumor growth and improved survival in xenograft animal models of neuroblastoma derived from the SK-N-AS cell lines. Our findings suggest that targeting LGR5 with RSPO2-based PDCs may offer a promising potential for treating neuroblastoma. Citation Format: Yukimatsu Toh. Targeting high-expression LGR5 by an R-spondin-based peptibody-drug conjugate is efficacious against neuroblastoma [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2023 Oct 11-15; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2023;22(12 Suppl):Abstract nr C098.

Preclinical Development of ADCT-601, a Novel Pyrrolobenzodiazepine Dimer-based Antibody-drug Conjugate Targeting AXL-expressing Cancers.

AXL, a tyrosine kinase receptor that is overexpressed in many solid and hematologic malignancies, facilitates cancer progression and is associated with poor clinical outcomes. Importantly, drug-induced expression of AXL results in resistance to conventional chemotherapy and targeted therapies. Together with its presence on multiple cell types in the tumor immune microenvironment, these features make it an attractive therapeutic target for AXL-expressing malignancies. ADCT-601 (mipasetamab uzoptirine) is an AXL-targeted antibody-drug conjugate (ADC) comprising a humanized anti-AXL antibody site specifically conjugated using GlycoConnect technology to PL1601, which contains HydraSpace, a Val-Ala cleavable linker and the potent pyrrolobenzodiazepine (PBD) dimer cytotoxin SG3199. This study aimed to validate the ADCT-601 mode of action and evaluate its efficacy in vitro and in vivo, as well as its tolerability and pharmacokinetics. ADCT-601 bound to both soluble and membranous AXL, and was rapidly internalized by AXL-expressing tumor cells, allowing release of PBD dimer, DNA interstrand cross-linking, and subsequent cell killing. In vivo, ADCT-601 had potent and durable antitumor activity in a wide variety of human cancer xenograft mouse models, including patient-derived xenograft models with heterogeneous AXL expression where ADCT-601 antitumor activity was markedly superior to an auristatin-based comparator ADC. Notably, ADCT-601 had antitumor activity in a monomethyl auristatin E-resistant lung-cancer model and synergized with the PARP inhibitor olaparib in a BRCA1-mutated ovarian cancer model. ADCT-601 was well tolerated at doses of up to 6 mg/kg and showed excellent stability in vivo. These preclinical results warrant further evaluation of ADCT-601 in the clinic.

ABCL-022: LOTIS-2 Follow-Up Analysis: Updated Results from a Phase 2 Study of Loncastuximab Tesirine (Lonca) in Relapsed or Refractory Diffuse Large B-Cell Lymphoma

Context Patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) who are ineligible for, or relapse after, salvage chemotherapy/stem cell transplant (SCT) have a poor prognosis. Lonca comprises a humanized anti-CD19 antibody conjugated to a potent pyrrolobenzodiazepine dimer toxin. Objective To assess updated efficacy and safety findings from a Phase 2 study evaluating Lonca in patients with R/R DLBCL (LOTIS-2; NCT03589469). Design Multicenter, open-label, single-arm Phase 2 study in adult patients (≥18 years) with pathologically defined R/R DLBCL and ≥2 prior systemic treatments. Intervention Lonca (150 µg/kg every 3 weeks [Q3W] for 2 cycles; 75 µg/kg Q3W thereafter). Main Outcomes Measures Primary efficacy endpoint: Overall response rate (ORR), assessed by central review. Secondary efficacy endpoints: Duration of response (DoR), progression-free survival (PFS), and overall survival (OS). Safety analyses: Treatment-emergent adverse events (TEAEs). Follow-up period: Q12W for ≤3 years after end of treatment. Results 145 patients with R/R DLBCL received ≥1 Lonca dose. Median age was 66 years (range 23–94). Patients received a median of 3 prior therapies (range 2–7). At data cut-off (October 26, 2020, ≥12 months since first dose), 2 patients continued treatment. Patients received a mean of 4.6 Lonca cycles (std 4.1; range 1–22). ORR was 48.3% (complete response [CR]: 24.8%; partial response [PR]: 23.4%). Median DoR was 12.6 months for patients with CR or PR (n=70); not reached for patients with CR. Median PFS and OS were 4.9 and 9.5 months, respectively. Post-Lonca treatment, 15 patients received CD19-directed chimeric antigen receptor T-cell therapy with an investigator-assessed ORR of 46.7%, and 11 patients proceeded to SCT as consolidation after Lonca response. Most common (≥25.0%) all-grade TEAEs were increased gamma-glutamyltransferase (41.4%), neutropenia (40.0%), thrombocytopenia (33.1%), fatigue (27.6%), and anemia (26.2%). Grade ≥3 TEAEs occurred in 107 (73.8%) patients. Treatment-related TEAEs leading to treatment discontinuation and dose delays occurred in 26 (17.9%) and 62 (42.8%) patients, respectively. Conclusions After longer follow-up of patients in LOTIS-2, durable responses to Lonca continue to be observed in heavily pre-treated patients with R/R DLBCL. No new safety concerns occurred. Research funding ADC Therapeutics SA.

Abstract 1366: Integrated population modeling of loncastuximab tesirine (Lonca) exposure in B-cell non-Hodgkin lymphoma (B-NHL)

Abstract Lonca is an antibody (Ab) drug conjugate comprising a humanized monoclonal Ab directed against B-cell antigen CD19, conjugated with a potent pyrrolobenzodiazepine (PBD) dimer toxin. In a Phase 1 (NCT02669017) study in relapsed or refractory (R/R) B-NHL, a recommended Phase 2 dosing regimen for Lonca of 150 µg/kg once every 3 weeks (Q3W) for two doses, followed by 75 µg/kg Q3W was identified then evaluated in a Phase 2 (NCT03589469) study in R/R diffuse large B-cell lymphoma (DLBCL). A population pharmacokinetic (PPK) model was developed to characterize the pharmacokinetics (PK) of the Lonca dosing regimen and evaluate exposure covariates. The integrated PPK model was used to describe drug concentrations for Lonca PBD-conjugated Ab (5,301 samples), total Ab (5,241 samples), and unconjugated warhead SG3199 (239 samples) in serum from 328 patients. Samples were taken pre-dose, at end of infusion and at pre-determined timepoints post-infusion throughout the trials. Analysis was performed using non-linear mixed-effects modeling (NONMEM, v7.4 [ICON Solutions]). Subgroup analyses were conducted on model-predicted exposure metrics derived from simulation of Lonca PK profiles based on empirical Bayesian estimates of individual PK parameters. Concentration-time data of Lonca PBD-conjugated Ab and total Ab were best characterized by a two-compartment model with parallel linear clearance (0.218 L/day), and a time-dependent clearance component which approached zero by ~15 weeks. The estimated volume of distribution of central compartment was 3.86 L and the estimated typical half-life at steady state of Lonca is ~3 weeks. The effect of body weight, age, sex, race, renal impairment, drug formulation, anti-drug Ab, ECOG, and concomitant P-gp inhibitors did not show clinically important influence on exposure (< ±30% change relative to reference). Based on model-predicted Cycle 1 average concentration (Cavg) patients with low albumin (<35 g/L, n=49) had 52% lower Cavg than patients with normal albumin levels (≥35 g/L, n=279). Patients with non-DLBCL (n=44) had 61% lower Cavg than patients with DLBCL (n=284). Trends of lower exposures with baseline mild/moderate hepatic impairment and ECOG status >1 were noted but did not appear to be of clinical relevance. In conclusion, Lonca exposure was well described by a two-compartment model with linear and time-dependent clearance; the latter is thought to reflect reduction of tumor cells. Lonca exposure was lower in non-DLBCL patients, and lower in patients with hypoalbuminemia secondary to enhanced protein clearance in patients with critical illness. Overall, modeling demonstrates rapid attainment of steady-state exposure for Lonca given 150 µg/kg Q3W for two doses, and a sustaining profile for Lonca given 75 µg/kg Q3W thereafter for patients with DLBCL. Citation Format: Melhem Solh, Juan Pablo Alderuccio, Anastasios Stathis, David Ungar, Sam Liao, Lisa Khouri, Xiaoyan Zhang, Joseph Boni. Integrated population modeling of loncastuximab tesirine (Lonca) exposure in B-cell non-Hodgkin lymphoma (B-NHL) [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 1366.

Interim Results from a Phase 1 Study of ADCT-301 (Camidanlumab Tesirine) Show Promising Activity of a Novel Pyrrolobenzodiazepine-Based Antibody Drug Conjugate in Relapsed/Refractory Hodgkin/Non-Hodgkin Lymphoma

Interim Results from a Phase 1 Study of ADCT-301 (Camidanlumab Tesirine) Show Promising Activity of a Novel Pyrrolobenzodiazepine-Based Antibody Drug Conjugate in Relapsed/Refractory Hodgkin/Non-Hodgkin Lymphoma

Duration of response to loncastuximab tesirine in relapsed/refractory diffuse large B-cell lymphoma by demographic and clinical characteristics: Subgroup analyses from LOTIS 2.

7546 Background: Outcomes for patients with refractory/relapsed diffuse large B-cell lymphoma (R/R DLBCL) are poor, particularly for those with high-risk clinical characteristics. There remains an unmet need for new treatment options for these patients. Loncastuximab tesirine (Lonca) is an antibody-drug conjugate comprising a humanized anti-CD19 antibody conjugated to a potent pyrrolobenzodiazepine dimer toxin. LOTIS 2 was a pivotal Phase 2 study that demonstrated substantial single-agent anti-cancer activity of Lonca in patients with R/R DLBCL. Efficacy and safety data were presented at ASH 2020 (Caimi et al, ASH 2020; abstract 1183). Here we present subgroup analyses of duration of response (DoR) to Lonca by demographic and clinical characteristics. Methods: Adult patients with R/R DLBCL who had received ≥2 prior therapies were enrolled in this Phase 2, multicenter, single-arm, open-label study of single-agent Lonca (150 µg/kg every 3 weeks for 2 doses, followed by 75 µg/kg thereafter for up to 1 year). The primary analysis has previously been reported, with a primary endpoint of overall response rate (ORR). Patients are being followed-up every 12 weeks for up to 3 years. DoR was a key secondary efficacy endpoint, defined as time from the first documentation of response (central review) to disease progression or death. We analyzed pre-specified demographic and clinical characteristic subgroups for DoR. Results: As of data cut-off (August 6, 2020), ORR in the total population (N = 145) was 48.3% (24.8% had complete response [CR] and 23.4% had partial response [PR]). Median DoR (mDoR) for the 70 responders was 12.58 months. mDoR for patients with CR and PR was 13.37 months and 5.68 months, respectively. Overall, subgroups with high-risk characteristics for poor prognosis had a DoR comparable to the whole study population. mDoR for patients with double-/triple-hit DLBCL was 13.37 months, with advanced stage disease was 12.58 months, and with transformed disease was 12.58 months. The mDoR for older patients was longer than for younger patients (≥75 years, 13.37 months; 65 to < 75 years, 12.58 months; < 65 years, 9.26 months). Patients with DLBCL refractory (defined as no response to therapy) to first-line, most recent line, and all prior lines of therapy had mDoRs of 9.63 months, 9.26 months, and 9.63 months, respectively. Conclusions: Durable responses were observed with the recommended Phase 2 dose regimen of Lonca in heavily pre-treated patients and those at high risk of poor prognosis, including older patients and those with double-/triple-hit, advanced stage, transformed, and primary refractory DLBCL. Updated DoR data will be presented at the meeting. Clinical trial information: NCT03589469.

Early Development, Scale-Up, and Reverse-Phase Purification of a Highly Potent Pyrrolobenzodiazepine Dimer, SG3259, for Use in Antibody–Drug Conjugates

Pyrrolobenzodiazepine (PBD) dimers, such as that found in SG3259, are fully synthetic highly potent (subnanomolar) small molecules currently being developed as warheads for antibody–drug conjugates...

A MET Targeting Antibody-Drug Conjugate Overcomes Gemcitabine Resistance in Pancreatic Cancer.

Pancreatic cancer is an aggressive disease associated with a poor 5-year overall survival. Most patients are ineligible for surgery due to late diagnosis and are treated primarily with chemotherapy with very limited success. Pancreatic cancer is relatively insensitive to chemotherapy due to multiple factors, including reduced bioavailability of drugs to tumor cells. One strategy to improve drug efficacy with reduced toxicity is the development of antibody-drug conjugates (ADC), which have now been used successfully to treat both solid and liquid tumors. Here, we evaluate the efficacy of TR1801-ADC, a newly developed ADC composed of a MET antibody conjugated to the highly potent pyrrolobenzodiazepine toxin-linker, tesirine. We first evaluated MET expression and subcellular localization in pancreatic cancer cell lines, human tumors, and patient-derived xenografts (PDX). We then tested TR1801-ADC efficacy in vitro in pancreatic cancer cell lines. Preclinical evaluation of TR1801-ADC efficacy was conducted on PDXs selected on the basis of their MET expression level. We show that MET is highly expressed and located at the plasma membrane of pancreatic cancer cells. We found that TR1801-ADC induces a specific cytotoxicity in pancreatic cancer cell lines and a profound tumor growth inhibition, even in a gemcitabine-resistant tumor. We also noted synergism between TR1801-ADC and gemcitabine in vitro and an improved response to the combination in vivo. Together, these results suggest the promise of agents such as TR1801-ADC as a novel approach to the treatment of pancreatic cancer.

Preliminary Results of a Phase 2 Study of Camidanlumab Tesirine (Cami), a Novel Pyrrolobenzodiazepine-Based Antibody-Drug Conjugate, in Patients with Relapsed or Refractory Hodgkin Lymphoma

Preliminary Results of a Phase 2 Study of Camidanlumab Tesirine (Cami), a Novel Pyrrolobenzodiazepine-Based Antibody-Drug Conjugate, in Patients with Relapsed or Refractory Hodgkin Lymphoma

Efficacy and Safety of Loncastuximab Tesirine (ADCT-402) in Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Efficacy and Safety of Loncastuximab Tesirine (ADCT-402) in Relapsed/Refractory Diffuse Large B-Cell Lymphoma

Targeting Multiple EGFR-expressing Tumors with a Highly Potent Tumor-selective Antibody-Drug Conjugate.

ABBV-321 (serclutamab talirine), a next-generation EGFR-targeted antibody-drug conjugate (ADC) incorporates a potent pyrrolobenzodiazepine (PBD) dimer toxin conjugated to the EGFR-targeting ABT-806 affinity-matured AM1 antibody. ABBV-321 follows the development of related EGFR-targeted ADCs including depatuxizumab mafodotin (depatux-m, ABT-414), ABT-806 conjugated to monomethyl auristatin F (MMAF), and ABBV-221 (losatuxizumab vedotin), AM1 antibody conjugated to monomethyl auristatin E (MMAE). The distinct tumor selectivity of ABBV-321 differentiates it from many previous highly active antibody PBD conjugates that lack a therapeutic window. Potency of the PBD dimer, combined with increased binding of AM1 to EGFR-positive tumor cells, opens the possibility to target a wide array of tumors beyond those with high levels of EGFR overexpression or amplification, including those insensitive to auristatin-based ADCs. ABBV-321 exhibits potent antitumor activity in cellular and in vivo studies including xenograft cell line and patient-derived xenograft glioblastoma, colorectal, lung, head and neck, and malignant mesothelioma tumor models that are less sensitive to depatux-m or ABBV-221. Combination studies with ABBV-321 and depatux-m suggest a promising treatment option permitting suboptimal, and potentially better tolerated, doses of both ADCs while providing improved potency. Collectively, these data suggest that ABBV-321 may offer an extended breadth of efficacy relative to other EGFR ADCs while extending utility to multiple EGFR-expressing tumor indications. Despite its highly potent PBD dimer payload, the tumor selectivity of ABBV-321, coupled with its pharmacology, toxicology, and pharmacokinetic profiles, support continuation of ongoing phase I clinical trials in patients with advanced EGFR-expressing malignancies.

Another disappointment in treating relapsed, refractory high-risk aggressive B-cell lymphomas.

Another disappointment in treating relapsed, refractory high-risk aggressive B-cell lymphomas.

An Anti–CLL-1 Antibody–Drug Conjugate for the Treatment of Acute Myeloid Leukemia

The treatment of acute myeloid leukemia (AML) has not significantly changed in 40 years. Cytarabine- and anthracycline-based chemotherapy induction regimens (7 + 3) remain the standard of care, and most patients have poor long-term survival. The reapproval of Mylotarg, an anti-CD33-calicheamicin antibody-drug conjugate (ADC), has demonstrated ADCs as a clinically validated option to enhance the effectiveness of induction therapy. We are interested in developing a next-generation ADC for AML to improve upon the initial success of Mylotarg. The expression pattern of CLL-1 and its hematopoietic potential were investigated. A novel anti-CLL-1-ADC, with a highly potent pyrrolobenzodiazepine (PBD) dimer conjugated through a self-immolative disulfide linker, was developed. The efficacy and safety profiles of this ADC were evaluated in mouse xenograft models and in cynomolgus monkeys. We demonstrate that CLL-1 shares similar prevalence and trafficking properties that make CD33 an excellent ADC target for AML, but lacks expression on hematopoietic stem cells that hampers current CD33-targeted ADCs. Our anti-CLL-1-ADC is highly effective at depleting tumor cells in AML xenograft models and lacks target independent toxicities at doses that depleted target monocytes and neutrophils in cynomolgus monkeys. Collectively, our data suggest that an anti-CLL-1-ADC has the potential to become an effective and safer treatment for AML in humans, by reducing and allowing for faster recovery from initial cytopenias than the current generation of ADCs for AML.

Phase 1 Study of Adct-301 (Camidanlumab Tesirine), a Novel Pyrrolobenzodiazepine-Based Antibody Drug Conjugate, in Relapsed/Refractory Classical Hodgkin Lymphoma

Phase 1 Study of Adct-301 (Camidanlumab Tesirine), a Novel Pyrrolobenzodiazepine-Based Antibody Drug Conjugate, in Relapsed/Refractory Classical Hodgkin Lymphoma

Adct-301 (Camidanlumab Tesirine), a Novel Pyrrolobenzodiazepine-Based CD25-Targeting Antibody Drug Conjugate, in a Phase 1 Study of Relapsed/Refractory Non-Hodgkin Lymphoma Shows Activity in T-Cell Lymphoma

Adct-301 (Camidanlumab Tesirine), a Novel Pyrrolobenzodiazepine-Based CD25-Targeting Antibody Drug Conjugate, in a Phase 1 Study of Relapsed/Refractory Non-Hodgkin Lymphoma Shows Activity in T-Cell Lymphoma

Fractionated Dosing Improves Preclinical Therapeutic Index of Pyrrolobenzodiazepine-Containing Antibody Drug Conjugates.

Purpose: To use preclinical models to identify a dosing schedule that improves tolerability of highly potent pyrrolobenzodiazepine dimers (PBDs) antibody drug conjugates (ADCs) without compromising antitumor activity.Experimental Design: A series of dose-fractionation studies were conducted to investigate the pharmacokinetic drivers of safety and efficacy of PBD ADCs in animal models. The exposure-activity relationship was investigated in mouse xenograft models of human prostate cancer, breast cancer, and gastric cancer by comparing antitumor activity after single and fractionated dosing with tumor-targeting ADCs conjugated to SG3249, a potent PBD dimer. The exposure-tolerability relationship was similarly investigated in rat and monkey toxicology studies by comparing tolerability, as assessed by survival, body weight, and organ-specific toxicities, after single and fractionated dosing with ADCs conjugated to SG3249 (rats) or SG3400, a structurally related PBD (monkeys).Results: Observations of similar antitumor activity in mice treated with single or fractionated dosing suggests that antitumor activity of PBD ADCs is more closely related to total exposure (AUC) than peak drug concentrations (Cmax). In contrast, improved survival and reduced toxicity in rats and monkeys treated with a fractionated dosing schedule suggests that tolerability of PBD ADCs is more closely associated with Cmax than AUC.Conclusions: We provide the first evidence that fractionated dosing can improve preclinical tolerability of at least some PBD ADCs without compromising efficacy. These findings suggest that preclinical exploration of dosing schedule could be an important clinical strategy to improve the therapeutic window of highly potent ADCs and should be investigated further. Clin Cancer Res; 23(19); 5858-68. ©2017 AACR.