Therapeutic Response of CCKBR-Positive Tumors to Combinatory Treatment with Everolimus and the Radiolabeled Minigastrin Analogue [177Lu]Lu-PP-F11N

Preclinical evaluation of 225Ac-labeled minigastrin analog DOTA-CCK-66 for Targeted Alpha Therapy

The recently developed metabolically more stable minigastrin derivative, DOTA-CCK-66, displayed promising preclinical data when labeled either with 68Ga or 177Lu. First positron emission tomography/computed tomography (PET/CT) imaging using [68Ga]Ga-DOTA-CCK-66 in two patients suffering from medullary thyroid carcinoma (MTC) displayed a favorable biodistribution profile. Here, we aim to investigate the therapeutic potential of [225Ac]Ac-DOTA-CCK-66 as a targeted α-therapy (TAT) agent in a comparative treatment study of [177Lu]Lu- versus [225Ac]Ac-DOTA-CCK-66.

METHODS

Treatment studies were performed (3 groups, n = 5, AR42J tumor-bearing 394-NOD SCID mice). Control group animals were injected with [68Ga]Ga-DOTA-CCK-66 (1.1 MBq, PET/CT imaging), while treatment group animals received a single dose of either [177Lu]Lu-DOTA-CCK-66 (37 MBq, radioligand therapy (RLT)) or [225Ac]Ac-DOTA-CCK-66 (37 kBq, TAT). All animals' tumor volume and body weight were monitored twice a week until end-point criteria were reached. Blood samples were evaluated (VetScan VS2, Abaxis) once mice were sacrificed.

RESULTS

Upon treatment, an initial decline in tumor volume, followed by a significantly delayed tumor growth of treated cohorts, was observed. Mean survival of 177Lu- as well as 225Ac-treated animals was increased by 3- (37 ± 3 d) and 4.5-fold (54 ± 6 d), respectively, when compared to non-treated animals (12 ± 3 d). Blood sample analysis did not indicate toxic side effects to the liver, kidney, or stomach upon 177Lu and 225Ac-treatment.

CONCLUSION

We demonstrated a substantial therapeutic efficacy of 177Lu- and 225Ac-labeled DOTA-CCK-66. As expected, treatment with the latter resulted in the highest mean survival rates. These results indicate a high therapeutic potential of 225Ac-labeled DOTA-CCK-66 for TAT in MTC patient management.

Detecting radio- and chemoresistant cells in 3D cancer co-cultures using chromatin biomarkers

The heterogenous treatment response of tumor cells limits the effectiveness of cancer therapy. While this heterogeneity has been linked to cell-to-cell variability within the complex tumor microenvironment, a quantitative biomarker that identifies and characterizes treatment-resistant cell populations is still missing. Herein, we use chromatin organization as a cost-efficient readout of the cells' states to identify subpopulations that exhibit distinct responses to radiotherapy. To this end, we developed a 3D co-culture model of cancer spheroids and patient-derived fibroblasts treated with radiotherapy. Using the model we identified treatment-resistant cells that bypassed DNA damage checkpoints and exhibited an aggressive growth phenotype. Importantly, these cells featured more condensed chromatin which primed them for treatment evasion, as inhibiting chromatin condensation and DNA damage repair mechanisms improved the efficacy of not only radio- but also chemotherapy. Collectively, our work shows the potential of using chromatin organization to cost-effectively study the heterogeneous treatment susceptibility of cells and guide therapeutic design.

Treatment strategies for clear cell renal cell carcinoma: Past, present and future

Clear cell renal cell carcinoma (ccRCC) is the most prevalent histological subtype of kidney cancer, which is prone to metastasis, recurrence, and resistance to radiotherapy and chemotherapy. The burden it places on human health due to its refractory nature and rising incidence rate is substantial. Researchers have recently determined the ccRCC risk factors and optimized the clinical therapy based on the disease's underlying molecular mechanisms. In this paper, we review the established clinical therapies and novel potential therapeutic approaches for ccRCC, and we support the importance of investigating novel therapeutic options in the context of combining established therapies as a research hotspot, with the goal of providing diversified therapeutic options that promise to address the issue of drug resistance, with a view to the early realization of precision medicine and individualized treatment.

Targeting mTORC1 Activity to Improve Efficacy of Radioligand Therapy in Cancer

Radioligand therapy (RLT) represents an effective strategy to treat malignancy by cancer-selective delivery of radioactivity following systemic application. Despite recent therapeutic successes, cancer radioresistance and insufficient delivery of the radioactive ligands, as well as cytotoxicity to healthy organs, significantly impairs clinical efficacy. To improve disease management while minimizing toxicity, in recent years, the combination of RLT with molecular targeted therapies against cancer signaling networks showed encouraging outcomes. Characterization of the key deregulated oncogenic signaling pathways revealed their convergence to activate the mammalian target of rapamycin (mTOR), in which signaling plays an essential role in the regulation of cancer growth and survival. Therapeutic interference with hyperactivated mTOR pathways was extensively studied and led to the development of mTOR inhibitors for clinical applications. In this review, we outline the regulation and oncogenic role of mTOR signaling, as well as recapitulate and discuss mTOR complex 1 (mTORC1) inhibition to improve the efficacy of RLT in cancer.

Nonpeptidic Z360-Analogs Tagged with Trivalent Radiometals as Anti-CCK2R Cancer Theranostic Agents: A Preclinical Study

(1) Background: Theranostic approaches in the management of cholecystokinin subtype 2 receptor (CCK₂R)-positive tumors include radiolabeled gastrin and CCK motifs. Moving toward antagonist-based CCK₂R-radioligands instead, we herein present three analogs of the nonpeptidic CCK₂R-antagonist Z360, GAS1/2/3. Each was conjugated to a different chelator (DOTA, NODAGA or DOTAGA) for labeling with medically relevant trivalent radiometals (e.g., Ga-68, In-111, Lu-177) for potential use as anti-CCK₂R cancer agents; (2) Methods: The in vitro properties of the thee analogs were compared in stably transfected HEK293-CCK₂R cells. Biodistribution profiles were compared in SCID mice bearing twin HEK293-CCK₂R and wtHEK293 tumors; (3) Results: The GAS1/2/3 analogs displayed high CCK₂R-affinity (lower nM-range). The radioligands were fairly stable in vivo and selectively targeted the HEK293-CCK₂R, but not the CCK₂R-negative wtHEK293 tumors in mice. Their overall pharmacokinetic profile was found strongly dependent on the radiometal-chelate. Results could be visualized by SPECT/CT for the [¹¹¹In]In-analogs; (4) Conclusions: The present study highlighted the high impact of the radiometal-chelate on the end-pharmacokinetics of a new series of Z360-based radioligands, revealing candidates with promising properties for clinical translation. It also provided the impetus for the development of a new class of nonpeptidic radioligands for CCK₂R-targeted theranostics of human cancer.