Thimet oligopeptidase (EC 3.4.24.15) activates CPI-0004Na, an extracellularly tumour-activated prodrug of doxorubicin

Anthracycline-induced cardiotoxicity – are we about to clear this hurdle?

Anthracyclines have contributed significantly to remarkable improvements in overall survival and are regarded as the most effective cytostatic drug for cancer treatment in various malignancies. However, anthracyclines are a significant cause of acute and chronic cardiotoxicity in cancer patients, and long-term cardiotoxicity can lead to death in about one-third of patients. Several molecular pathways have been implicated in the development of anthracycline-induced cardiotoxicity, although the underlying mechanisms of some molecular pathways are not fully elucidated. It is now generally believed that anthracycline-induced reactive oxygen species (resulting from intracellular metabolism of anthracyclines) and drug-induced inhibition of topoisomerase II beta are the key mechanisms responsible for the cardiotoxicity. To prevent cardiotoxicity, several strategies are being followed: (i) angiotensin-converting enzyme inhibitors, sartans, beta-blockers, aldosterone antagonists, and statins; (ii) iron chelators; and (iii) by development of new anthracycline derivatives with little or no cardiotoxicity. This review will discuss clinically evaluated doxorubicin analogues that were developed as potentially non-cardiotoxic anticancer agents and include recent development of a novel liposomal anthracycline (L-Annamycin) for the treatment of soft-tissue sarcoma metastatic to the lung and acute myelogenous leukaemia.

PhAc-ALGP-Dox, a Novel Anticancer Prodrug with Targeted Activation and Improved Therapeutic Index

Clinical use of doxorubicin (Dox) is limited by cumulative myelo- and cardiotoxicity. This research focuses on the detailed characterization of PhAc-ALGP-Dox, a targeted tetrapeptide prodrug with a unique dual-step activation mechanism, designed to circumvent Dox-related toxicities and is ready for upcoming clinical investigation. Coupling Dox to a phosphonoacetyl (PhAc)-capped tetrapeptide forms the cell-impermeable, inactive compound, PhAc-ALGP-Dox. After extracellular cleavage by tumor-enriched thimet oligopeptidase-1 (THOP1), a cell-permeable but still biologically inactive dipeptide-conjugate is formed (GP-Dox), which is further processed intracellularly to Dox by fibroblast activation protein-alpha (FAPα) and/or dipeptidyl peptidase-4 (DPP4). In vitro, PhAc-ALGP-Dox is effective in various 2D- and 3D-cancer models, while showing improved safety toward normal epithelium, hematopoietic progenitors, and cardiomyocytes. In vivo, these results translate into a 10-fold higher tolerability and 5-fold greater retention of Dox in the tumor microenvironment compared with the parental drug. PhAc-ALGP-Dox demonstrates 63% to 96% tumor growth inhibition in preclinical models, an 8-fold improvement in efficacy in patient-derived xenograft (PDX) models, and reduced metastatic burden in a murine model of experimental lung metastasis, improving survival by 30%. The current findings highlight the potential clinical benefit of PhAc-ALGP-Dox, a targeted drug-conjugate with broad applicability, favorable tissue biodistribution, significantly improved tolerability, and tumor growth inhibition at primary and metastatic sites in numerous solid tumor models.

Combretastatin A4 Nanodrug-Induced MMP9 Amplification Boosts Tumor-Selective Release of Doxorubicin Prodrug

Tumor-associated enzyme-activated prodrugs can potentially improve the selectivity of chemotherapeutics. However, the paucity of tumor-associated enzymes which are essential for prodrug activation usually limits the antitumor potency. A cooperative strategy that utilizes combretastatin A4 nanodrug (CA4-NPs) and matrix metalloproteinase 9 (MMP9)-activated doxorubicin prodrug (MMP9-DOX-NPs) is developed. CA4 is a typical vascular disrupting agent that can selectively disrupt immature tumor blood vessels and exacerbate the tumor hypoxia state. After treatment with CA4-NPs, MMP9 expression can be significantly enhanced by 5.6-fold in treated tumors, which further boosts tumor-selective active drug release of MMP9-DOX-NPs by 3.7-fold in an orthotopic 4T1 mammary adenocarcinoma mouse model. The sequential delivery of CA4-NPs and MMP9-DOX-NPs exhibits enhanced antitumor efficacy with reduced systemic toxicity compared with the noncooperative controls.

First-in-man phase I study assessing the safety and pharmacokinetics of a 1-hour intravenous infusion of the doxorubicin prodrug DTS-201 every 3 weeks in patients with advanced or metastatic solid tumours

PURPOSE

DTS-201 is a doxorubicin (Dox) prodrug that shows encouraging data in experimental models in terms of both efficacy and safety compared with conventional Dox. The purpose of this phase I study was to assess the safety profile, to establish the recommended dose (RD) for clinical phase II studies and to assess potential anticancer activity of the compound.

EXPERIMENTAL DESIGN

DTS-201 was administered as a 1-hour infusion every 3 weeks in eligible patients with advanced solid tumours according to common clinical phase I criteria. Dose escalation was performed according to a modified Fibonacci schema.

RESULTS

Twenty-five patients with a median age of 58 years (range, 30-72) were enrolled in the study. The median number of treatment cycles was 2 (range, 1-8). DTS-201 was administered at four dose levels (DLs) ranging from 80 to 400 mg/m², which is equivalent to 45-225 mg/m² of conventional Dox. No dose-limiting toxicity (DLT) occurred at the first two DLs. Three DLTs were observed at DL3 and DL4 (diarrhoea for DL3, vomiting and neutropenia for DL4). DL4 (400 mg/m²) was considered the maximum tolerated dose. Myelosuppression was the main toxicity, and NCI-CTC grade III-IV neutropenia was common at RD. Non-haematological adverse reactions were mild to moderate and included nausea, anorexia, asthenia and alopecia. No treatment-related severe cardiac adverse events were observed.

CONCLUSIONS

DTS-201 is well tolerated and safe in heavily pretreated solid tumour patients. A high equivalent dose of Dox could be delivered without severe drug-related cardiac events. DTS-201 showed evidence of clinical activity with a confirmed partial response in a patient with soft-tissue sarcoma. The recommended phase II dose is 400 mg/m².

Expression of THOP1 and its relationship to prognosis in non-small cell lung cancer

BACKGROUND

The study was designed to detect the expression level of thimet oligopeptidase (THOP1) protein in non-small cell lung cancer (NSCLC) and investigate its correlation with clinicopathologic features and prognosis.

METHODS

Immunohistochemical staining was used to determine the expression of THOP1 protein in 120 NSCLC specimens and 53 distant normal lung tissues. Quantitative real-time PCR and western blotting were employed to measure the expression of THOP1 in 16 pairs of primary NSCLC and corresponding normal tissues.

RESULTS

Analysis of immunohistochemical staining suggested low THOP1 expression was found in 71 (59.2%) of the 120 NSCLC specimens and significantly correlated with positive lymph node metastasis (P = 0.048). However, low THOP1 expression was found in 22 (41.5%) of the 53 normal lung tissues. Chi-square test suggested that the expression of THOP1 was significantly higher in the normal lung tissues than that in the NSCLC specimens (P = 0.032). Real-Time PCR and western blotting showed that NSCLC specimens had decreased THOP1 mRNA and protein expression compared to corresponding normal tissues. Univariate analysis demonstrated that low THOP1 expression significantly predicted decreased 5-year disease-free survival (P = 0.038) and overall survival (P = 0.017). In addition, positive lymph node metastasis (P = 0.025) and advanced TNM stage (P = 0.009) significantly predicted decreased 5-year overall survival. However, multivariate Cox regression analysis showed that only low THOP1 expression retained its significance as an independent prognostic factor for unfavorable 5-year disease-free survival (P = 0.046) and overall survival (P = 0.021).

CONCLUSIONS

THOP1 may have clinical potentials to be employed as a promising biomarker to identify individuals with better prognosis and a novel antitumor agent for therapy of patients with NSCLC.

Protease-activated drug development

In this extensive review, we elucidate the importance of proteases and their role in drug development in various diseases with an emphasis on cancer. First, key proteases are introduced along with their function in disease progression. Next, we link these proteases as targets for the development of prodrugs and provide clinical examples of protease-activatable prodrugs. Finally, we provide significant design considerations needed for the development of the next generation protease-targeted and protease-activatable prodrugs.

Preclinical toxicity, toxicokinetics, and antitumoral efficacy studies of DTS-201, a tumor-selective peptidic prodrug of doxorubicin

PURPOSE

There is a clear clinical need for cytotoxic drugs with a lower systemic toxicity. DTS-201 (CPI-0004Na) is a peptidic prodrug of doxorubicin that shows an improved therapeutic index in experimental models. The purpose of the current study was to complete its preclinical characterization before initiation of phase I clinical trials.

EXPERIMENTAL DESIGN

The preclinical development program consisted of a detailed assessment of the general and cardiac toxicity profiles of DTS-201 in mice, rats, and dogs, together with mass balance and antitumoral efficacy studies in rodents. Neprilysin and thimet oligopeptidase expression, two enzymatic activators of DTS-201, was also characterized in human breast and prostate tumor biopsies.

RESULTS

The target organs of DTS-201 toxicity in rodents and dogs are typically those of doxorubicin, albeit at much higher doses. Importantly, chronic treatment with DTS-201 proved to be significantly less cardiotoxic than with doxorubicin at doses up to 8-fold higher in rats. The mass balance study showed that [14C] DTS-201 does not accumulate in the body after intravenous administration. The improved therapeutic index of DTS-201 compared with free doxorubicin was confirmed in three tumor xenograft models of prostate, breast, and lung cancer. Neprilysin and/or thimet oligopeptidase are expressed in all experimental human tumor types thus far tested as well as in a large majority of human breast and prostate tumor biopsies.

CONCLUSION

DTS-201 gave promising results in terms of general toxicity, cardiovascular tolerance, and in vivo efficacy in xenograft mouse models compared with free doxorubicin. Taken together, these results and the confirmation of the presence of activating enzymes in human tumor biopsies provide a strong rationale for a phase I clinical study in cancer patients.