Camptothecin

Trastuzumab deruxtecan (T-DXd) intracranial activity has been observed in small or retrospective patient cohorts with human epidermal growth factor receptor 2-positive (HER2+) advanced/metastatic breast cancer (mBC) and stable or active (untreated/previously treated and progressing) brain metastases (BMs). The phase 3b/4 DESTINY-Breast12 study investigated T-DXd in patients with HER2+ mBC and is, to our knowledge, the largest prospective study of T-DXd in patients with BMs in this setting. Patients (stable/active BMs (n = 263) and no BMs (n = 241)) treated with one or more prior anti-HER2-based regimens received T-DXd (5.4 mg per kg). Primary endpoints were progression-free survival (PFS; BMs cohort) and objective response rate (ORR) per Response Evaluation Criteria in Solid Tumors version 1.1 (non-BMs cohort). Additional endpoints included central nervous system (CNS) PFS, ORR, time to second progression, CNS ORR (BMs cohort), incidence of new symptomatic CNS metastases (non-BMs cohort), time to progression, duration of response, overall survival and safety (both cohorts). No formal hypothesis testing was conducted for this single-arm, open-label study. In the BMs cohort, 12-month PFS was 61.6% (95% confidence interval (CI): 54.9-67.6), and 12-month CNS PFS was 58.9% (95% CI: 51.9-65.3). In the non-BMs cohort, ORR was 62.7% (95% CI: 56.5-68.8). Grade 3 or higher adverse events occurred in 51% (BMs cohort) and 49% (non-BMs cohort) of patients. Investigator-reported interstitial lung disease/pneumonitis occurred in 16% (grade ≥3: 3%) of patients with BMs and 13% (grade ≥3: 1%) of patients without BMs. These data show substantial and durable overall and intracranial activity for T-DXd, supporting its use in previously treated patients with HER2+ mBC irrespective of stable/active baseline BMs. ClinicalTrials.gov identifier: NCT04739761 .

Trastuzumab deruxtecan (T-DXd) showed statistically significant clinical improvement in patients with human epidermal growth factor receptor 2-positive (HER2+) gastric cancer in the DESTINY-Gastric01 trial. Exploratory results from DESTINY-Gastric01 suggested a potential benefit in patients with HER2-low gastric cancer. Spatial and temporal heterogeneity in HER2 expression or gene alteration, an inherent characteristic of gastric cancer tumors, presents a challenge in identifying patients who may respond to T-DXd. Specific biomarkers related to therapeutic response have not been explored extensively. Exploratory analyses were conducted to assess baseline HER2-associated biomarkers in circulating tumor DNA and tissue samples, and to investigate mechanisms of resistance to T-DXd. Baseline HER2-associated biomarkers were correlated with objective response rate (ORR) in the primary cohort of patients with HER2+ gastric cancer. The primary cohort had 64% concordance between HER2 positivity and HER2 (ERBB2) plasma gene amplification. Other key driver gene amplifications, specifically MET, EGFR and FGFR2, in circulating tumor DNA were associated with numerically lower ORR. Among 12 patients with HER2 gain-of-function mutations, ORR was 58.3% (7 of 12). ORR was consistent regardless of timing of immunohistochemistry sample collection. Further investigations are required in larger studies.

Resistance to chemotherapy has been a major hurdle that limits therapeutic benefits for many types of cancer. Here we systematically identify genetic drivers underlying chemoresistance by performing 30 genome-scale CRISPR knockout screens for seven chemotherapeutic agents in multiple cancer cells. Chemoresistance genes vary between conditions primarily due to distinct genetic background and mechanism of action of drugs, manifesting heterogeneous and multiplexed routes towards chemoresistance. By focusing on oxaliplatin and irinotecan resistance in colorectal cancer, we unravel that evolutionarily distinct chemoresistance can share consensus vulnerabilities identified by 26 second-round CRISPR screens with druggable gene library. We further pinpoint PLK4 as a therapeutic target to overcome oxaliplatin resistance in various models via genetic ablation or pharmacological inhibition, highlighting a single-agent strategy to antagonize evolutionarily distinct chemoresistance. Our study not only provides resources and insights into the molecular basis of chemoresistance, but also proposes potential biomarkers and therapeutic strategies against such resistance.

The plant alkaloid camptothecin is a high-value precursor for the semi-synthesis of multiple anticancer drugs. The key transformation during its biosynthetic pathway is a yet enigmatic skeletal reorganization from a 6/5/6 tetrahydro-β-carboline ring system to the 6/6/5 pyrroloquinoline scaffold, which is characteristic of camptothecin-related alkaloids. Here, we show that this scaffold transition can be efficiently catalyzed by flavin cofactors such as flavin mononucleotide in a photooxidative process. As part of this complex transformation, we verified the existence of a previously postulated macrocyclic ketolactam intermediate. Based on the mild conditions-oxygen, light, and flavins-we show that this conversion can also take place in leaves of Nicotiana benthamiana, a plant which does not normally produce camptothecin or related alkaloids. Our optimized biomimetic photochemical reaction conditions enable a short, mild, and efficient semi-synthesis of the alkaloids (3S)-pumiloside, (3R)-pumiloside, and vincosamide ketolactam, also known as turpiniside, without any protecting groups. Thus, our work improves our understanding of this key skeletal reorganization step forming the camptothecin scaffold in nature and provides streamlined photocatalytic access to camptothecin-related alkaloids.