Validity of Anti-PSMA ScFvD2B as a Theranostic Tool: A Narrative-Focused Review

Nanobody-enhanced chimeric antigen receptor T-cell therapy: overcoming barriers in solid tumors with VHH and VNAR-based constructs

CAR-T cells are genetically modified T lymphocytes that express chimeric antigen receptors (CAR) on their surfaces. These receptors enable T lymphocytes to recognize specific antigens on target cells, triggering a response that leads to targeted cytotoxicity. While CAR-T therapy has effectively treated various blood cancers, it faces significant challenges in addressing solid tumors. These challenges include identifying precise tumor antigens, overcoming antigen evasion, and enhancing the function of CAR-T cells within the tumor microenvironment. Single domain antibody, versatile tools with low immunogenicity, high stability, and strong affinity, show promise for improving the efficacy of CAR-T cells against solid tumors. By addressing these challenges, single domain antibody has the potential to overcome the limitations associated with ScFv antibody-based CAR-T therapies. This review highlights the benefits of utilizing single domain antibody in CAR-T therapy, particularly in targeting tumor antigens, and explores development strategies that could advance the field.

Development and Characterization of 99mTc-scFvD2B as a Potential Radiopharmaceutical for SPECT Imaging of Prostate Cancer

Previously, we demonstrated that the 177Lu-labeled single-chain variable fragment of an anti-prostate-specific membrane antigen (PSMA) IgG D2B antibody (scFvD2B) showed higher prostate cancer (PCa) cell uptake and tumor radiation doses compared to 177Lu-labeled Glu-ureide-based PSMA inhibitory peptides. To obtain a 99mTc-/177Lu-scFvD2B theranostic pair, this research aimed to synthesize and biochemically characterize a novel 99mTc-scFvD2B radiotracer. The scFvD2B-Tag and scFvD2B antibody fragments were produced and purified. Then, two HYNIC derivatives, HYNIC-Gly-Gly-Cys-NH2 (HYNIC-GGC) and succinimidyl-HYNIC (S-HYNIC), were used to conjugate the scFvD2B-Tag and scFvD2B isoforms, respectively. Subsequently, chemical characterization, immunoreactivity tests (affinity and specificity), radiochemical purity tests, stability tests in human serum, cellular uptake and internalization in LNCaP(+), PC3-PIP(++) or PC3(-) PCa cells of the resulting unlabeled HYNIC-scFvD2B conjugates (HscFv) and 99mTc-HscFv agents were performed. The results showed that incorporating HYNIC as a chelator did not affect the affinity, specificity or stability of scFvD2B. After purification, the radiochemical purity of 99mTc-HscFv radiotracers was greater than 95%. A two-sample t-test of 99mTc-HscFv1 and 99mTc-HscFv1 uptake in PC3-PIP vs. PC3 showed a p-value < 0.001, indicating that the PSMA receptor interaction of 99mTc-HscFv agents was statistically significantly higher in PSMA-positive cells than in the negative controls. In conclusion, the results of this research warrant further preclinical studies to determine whether the in vivo pharmacokinetics and tumor uptake of 99mTc-HscFv still offer sufficient advantages over HYNIC-conjugated peptides to be considered for SPECT/PSMA imaging.