Preclinical evaluation of BRP-020063, a first-in-class peptide based radiopharmaceutical for the treatment of nectin4-positive cancers

Background: Nectin-4 is aberrantly overexpressed in multiple solid tumors (e.g., bladder, breast, and non-small cell lung cancers, etc.), while showing limited expression in normal tissues. ‌This specific expression reveals that it is a promising drug target for Radionuclide Drug Conjugates (RDC). Here, we describe the preclinical evaluation of BRP-020063, a novel peptide binder based RDC with excellent drug-like properties. Methods: The protein binding affinity and selectivity of BRP-020063 were determined by surface plasmon resonance (SPR). Cell binding and internalization were characterized in PC3 cells engineered to express human Nectin4 (PC3-Nectin4) by radioligand binding assays using 177 Lu[Lu]-BRP-020063. Both of SPECT/CT imaging and ex vivo biodistribution studies in PC3-Nectin4 tumor-bearing mice were performed to evaluate the pharmacokinetics of 177 Lu[Lu]-BRP-020063. In addition, in vivo antitumor efficacy studies of 177 Lu[Lu]-BRP-020063 were also performed in the same cell derived xenograft (CDX) model to assess the therapeutic effect. Results: SPR studies showed BRP-020063 exhibited picomolar to nanomolar binding affinity to Nectin4 protein of human, mouse, rat, and cynomolgus monkey, and no binding to other members of the human Nectin-family (hNectins1-3, K D > 10 μmol/L). Potent cellular binding was confirmed in PC3-Nectin4 cells with nanomolar affinity. Cell uptake studies on PC3-Nectin4 cells and parent PC3 cells (PC3-WT) showed 177 Lu[Lu]-BRP-020063 specific bound to Nectin4. Meanwhile, 177 Lu[Lu]-BRP-020063 gave efficient internalization on PC3-Nectin4 cells. The SPECT/CT imaging of 177 Lu[Lu]-BRP-020063 demonstrated high tumor uptake and long-term tumor retention. The tumor uptake reached the peak (54.91±6.43% ID/g) at 24 h post-injection, and still remained 6.22±1.31% ID/g at 240 h post-injection. Ex vivo biodistribution studies further confirmed the remarkably robust and sustained tumor uptake of 177 Lu[Lu]-BRP-020063, the tumor uptake reached the inspiring 61.18±9.96% ID/g at 24 h post-injection, and maintained 25.50±5.10% ID/g at 72 h post-injection. The resulting tumor-to-kidney ratios were 2.34 at 24 h and 2.15 at 72 h post-injection. In addition, a single dose of 0.5 mCi or 1 mCi 177 Lu[Lu]-BRP-020063 per mouse led to robust and sustained tumor regression and prolonged animal survival. Conclusion: The preclinical in vitro and in vivo data demonstrate that 177 Lu[Lu]-BRP-020063 possesses excellent target specificity, favorable pharmacokinetic properties, and potent antitumor efficacy. These findings strongly support further investigation of the novel therapeutic 177 Lu[Lu]-BRP-020063 as a treatment for patients with Nectin4-positive solid tumors.