BEGONIA: Phase 1b/2, open-label, platform study of the safety and efficacy of durvalumab (D) ± paclitaxel (P) with novel oncology therapies for first-line metastatic triple-negative breast cancer (mTNBC): Addition of arm 7, D + datopotamab deruxtecan (Dato-DXd; DS-1062).

TPS1105 Background: Patients (pts) with mTNBC have limited treatment options and poor prognosis. The combination of immune checkpoint inhibitors with chemotherapy shows promise, but only a subset of pts with mTNBC derive benefit, highlighting the need for new combinations. BEGONIA is an ongoing Simon 2-stage, multicenter, multi-arm platform study evaluating the safety and efficacy of D, an anti–PD-L1 monoclonal antibody, with or without P, in combination with novel oncology therapies as first-line treatment for mTNBC (NCT03742102). Dato-DXd is an antibody-drug conjugate (ADC) consisting of a humanized anti-trophoblast cell surface antigen 2 (TROP2) IgG1 monoclonal antibody, a stable tetrapeptide-based cleavable linker, and a topoisomerase I inhibitor payload. Dato-DXd displayed encouraging clinical activity with a manageable safety profile in heavily pretreated pts with metastatic NSCLC in the phase 1 TROPION-PanTumor01 (NCT03401385) study. TROP2 is highly expressed on breast and other epithelial tumors, and a TROP2 ADC showed activity in heavily pretreated pts with mTNBC (Bardia, NEJM 2019). Methods: Eligible female pts are aged ≥18 years with untreated unresectable, locally advanced or mTNBC, ≥12 months since prior taxane therapy, ECOG PS 0/1, adequate organ function, and ≥1 nonirradiated measurable lesion. For Arm 7, pts are excluded if they have clinically significant corneal disease, history of interstitial lung disease/pneumonitis, underlying pulmonary disorder, or prior treatment with an ADC containing a topoisomerase I inhibitor. Arm 7 will evaluate D (1120 mg) + Dato-DXd (6 mg/kg) given intravenously every 3 weeks until disease progression or unacceptable toxicity. Part 1 of each arm includes a total of 30 pts with a safety run-in (n=6) to observe dose-limiting toxicities, identify the recommended phase 2 dose (RP2D), and detect an efficacy signal for part 1 expansion. The primary endpoint of part 1 is safety and tolerability. Secondary endpoints include investigator-assessed objective response rate (ORR), duration of response, progression-free survival (PFS), and overall survival (OS). Once the RP2D has been established for part 1, a futility analysis will be performed with an option to expand the cohort to an additional 27 pts if expansion criteria are met. The primary endpoint for part 1 is ORR. Tumors will be assessed every 6 weeks per RECIST v1.1. Kaplan-Meier analysis will be used for PFS and OS. PD-L1 and TROP2 expression will be assessed by immunohistochemistry. Enrollment is ongoing. Clinical trial information: NCT03742102 .

Efficacy of DAN-222, a novel investigational polymeric nanoparticle with topoisomerase I inhibitor, as monotherapy in breast cancer models and when combined with PARP inhibitor.

1081 Background: Patients with BRCA-positive HER2-negative breast cancer benefit from PARP inhibitor therapy, but additional benefit is still desired. PARP inhibition alone does not prevent all mechanisms for repairing damage to DNA such as homologous recombination repair. An attractive combination for treating such patients would be combining a topoisomerase I inhibitor with a PARP inhibitor given the dual mechanism this would provide for DNA damage and inhibited repair, leading to tumor cell death. This combination has been tried in multiple phase 1 studies, but myelotoxicity prevented the combination from being evaluated further. DAN-222 is a novel investigational polymeric nanoparticle conjugated with camptothecin, a topoisomerase I inhibitor, that provides significant accumulation of drug in tumor tissues via the enhanced permeability and retention (EPR) effect and significantly reduced bone marrow exposure compared to native chemotherapy. These observations underscore the potential advantages of DAN-222 alone as well as in combination with other agents such as PARP inhibitors in solid tumors. Here, we report the effects of DAN-222 monotherapy and in combination with a PARP inhibitor on the growth inhibition in an HRD+ TNBC breast cancer (MDA-MB-436) and an HRD- ovarian (OVCAR3) xenograft mouse model. Methods: HRD+ breast cancer tumor cells (MDA-MB-436) were implanted into female NCr nu/nu mice and HRD- ovarian cancer tumor cells (OVCAR3) were implanted into female CB.17 SCID mice. Mice were randomized to vehicle or treatment arms until tumors reached 2000 mm3 or day 45 (MDA-MB-436) or 1000mm3 or day 45 (OVCAR3). The groups evaluated include multiple dose levels of DAN-222 as monotherapy and those also combined with niraparib. Results: Results were consistent in both the HRD+ and HRD- tumor models with profound dose-response of DAN-222 monotherapy inhibiting tumor growth. Additionally, synergy was demonstrated when DAN-222 was combined with niraparib, clearly evident with low doses of both products when used in combination. The table below highlights the synergy of the combination of DAN-222 at 0.3 mg/kg and niraparib at 25 mg/kg above each agent alone on the tumor growth inhibition in the MDA-MB-436 xenograft. Conclusions: Combining a PARP inhibitor with a topoisomerase I inhibitor delivered via this polymeric nanoparticle delivery system (DAN-222) has synergistic efficacy in both HRD+ and HRD- xenograft tumor models. These data support continued development of DAN-222 to treat solid tumors and its combination use with PARP inhibitors.[Table: see text]

Immunogenic Cell Death by the Novel Topoisomerase I Inhibitor TLC388 Enhances the Therapeutic Efficacy of Radiotherapy

Rectal cancer accounts for 30–40% of colorectal cancer (CRC) and is the most common cancer-related death worldwide. The preoperative neoadjuvant chemoradiotherapy (neoCRT) regimen is the main therapeutic strategy for patients with locally advanced rectal cancer (LARC) to control tumor growth and reduce distant metastasis. However, 30–40% of patients achieve a partial response to neoCRT and suffer from unnecessary drug toxicity side effects and a risk of distant metastasis. In our study, we found that the novel topoisomerase I inhibitor lipotecan (TLC388) can elicit immunogenic cell death (ICD) to release damage-associated molecular patterns (DAMPs), including HMGB1, ANXA1, and CRT exposure. Lipotecan thereby increases cancer immunogenicity and triggers an antitumor immune response to attract immune cell infiltration within the tumor microenvironment (TME) in vitro and in vivo. Taken together, these results show that lipotecan can remodel the tumor microenvironment to provoke anticancer immune responses, which can provide potential clinical benefits to the therapeutic efficacy of neoCRT in LARC patients.