Structure–Activity Relationships of JMV4463, a Vectorized Cathepsin D Inhibitor with Antiproliferative Properties: The Unique Role of the AMPA‐Based Vector

Abstract

Cathepsin D (CathD) is overexpressed and secreted by several solid tumors and stimulates their growth, the mechanism of which is still not understood. In this context, the pepstatin bioconjugate JMV4463 [Ac-arg-O2 Oc-(Val)3-Sta-Ala-Sta-(AMPA)4-NH2; O2 Oc=8-amino-3,6-dioxaoctanoyl, Sta=statine, AMPA=ortho-aminomethylphenylacetyl], containing a new kind of cell-penetrating vector, was previously shown to exhibit potent antiproliferative effects in vitro and to delay the onset of tumors in vivo. In this study, we performed a structure-activity relationship analysis to evaluate the significance of the inhibitor and vector moieties of JMV4463. By modifying both statine residues of pepstatin we found that the antiproliferative activity is correlated with CathD inhibition, supporting a major role of the catalytic activity of intracellular CathD in cancer cell proliferation. Replacing the vector composed of four AMPA units with other vectors was found to abolish cytotoxicity, although all of the conjugates enabled pepstatin transport into cells. In addition, the AMPA4 vector must be localized at the C terminus of the bioconjugate. The unexpected importance of the vector structure and position for cytotoxic action suggests that AMPA4 enables pepstatin to inhibit the proteolysis of critical CathD substrates involved in cell proliferation via a unique mechanism of action.

Expression of Cathepsin D in early-stage breast cancer and its prognostic and predictive value

“…Prior studies have noted that Cathepsin D is involved in degradation of extracellular matrix and basement membrane in cancers due to its proteolytic activity [ 29 ]. A study using a vectorized Cathepsin D inhibitor found that anti-proliferative activity was associated with Cathepsin D inhibition, suggesting that intracellular Cathepsin D plays a major role in cancer cell proliferation [ 30 ].…”

Protease-triggered bioresponsive drug delivery for the targeted theranostics of malignancy

“…This chemically stable conjugate could be efficiently ingested by retinal cells and exhibited cathepsin D-accelerated drug release and targeted therapy for ocular diseases. Another approach focused on the vectorization of cathepsin D inhibitors and the interpretation of their structure-function relevance 286 , 287 . For cathepsin E, recent studies emphasized exploring its feasibility as a molecular target for cancer theranostics and developing its clinical application potency 288 .…”

Cyanobacterial peptides as a prototype for the design of cathepsin D inhibitors

“…However, the poor intracellular penetration of pepstatin A strictly limited its use on cancer cells. To overcome this drawback, a pepstatin bioconjugation was designed and showed satisfactory results on tumor cells and mice xenografted with breast cancer cells [20,21]. In our efforts to explore cyanobacterial peptides as a source of novel drug candidates [22][23][24][25][26][27][28], we have finished the total synthesis and structural reassignment of tasiamide B [28], which contained a statine-like unit (4-amino-3-hydroxy-5phenylpentanoic acid, Ahppa).…”