A phase 1B/2 study of aldoxorubicin in patients with soft tissue sarcoma

Aldoxorubicin in soft tissue sarcomas

Aldoxorubicin is a prodrug formulation of doxorubicin currently under investigation for the treatment of soft tissue sarcomas. Early studies have demonstrated a promising reduction in the cardiotoxicity of aldoxorubicin compared with equivalent doses of doxorubicin leading to an increase in the equivalent cumulative dose of aldoxorubicin. The current clinical and pharmacological data available for aldoxorubicin are extremely promising for its use in the treatment of advanced and metastatic soft tissue sarcomas compared with equivalent doses of doxorubicin although Phase III data are lacking. We review aldoxorubicin for the treatment of advanced and metastatic soft tissue sarcomas and discuss the impact it may have in the future.

Spotlight on aldoxorubicin (INNO-206) and its potential in the treatment of soft tissue sarcomas: evidence to date

Anthracyclines, and doxorubicin in particular, remain a mainstay of sarcoma therapy. Despite modest activity and significant toxicities, no cytotoxic monotherapy has yet yielded superior overall survival over doxorubicin for therapy of advanced soft tissue sarcomas in a randomized trial. Similarly, combination regimens have also been unable to overcome doxorubicin in terms of overall survival. Strategies to ameliorate the most prominent side effect of doxorubicin, cardiotoxicity, are available, but their use in sarcoma patients has been limited. Aldoxorubicin is a prodrug consisting of doxorubicin with a covalent linker. It binds rapidly after intravenous infusion to cysteine-34 of human serum albumin. The drug-albumin conjugate is preferentially retained in tumor tissue, with uptake into tumoral cells. At physiologic pH, the complex is stable. Hydrolysis can occur under the acidic conditions of the endocytic lysosome, releasing doxorubicin. Doxorubicin then distributes to various cellular compartments, including Golgi, mitochondrion, and nucleus, with subsequent cytotoxic effects. Aldoxorubicin has demonstrated in vitro and in vivo activities in both cancer model systems and human xenografts. Preclinical models also support its decreased cardiac effects vs doxorubicin, although such promising results require formal comparison at efficacy equivalent doses of the two drugs. Phase I studies confirmed the tolerability of aldoxorubicin in humans. Clinical cardiotoxicity was not observed, but molecular and subclinical cardiac effects could be demonstrated. A Phase II study in treatment-naïve, advanced sarcoma patients demonstrated improved progression-free survival and response rate over doxorubicin, although no survival benefit was evident. A Phase III study of aldoxorubicin vs investigator's choice from a panel of chemotherapy regimens in the salvage setting was unable to demonstrate a benefit in progression-free or overall survival in the entire population. Progression-free survival in L-sarcomas (leiomyosarcomas and liposarcomas) was documented. While evidence of subclinical cardiac effects was seen in a small proportion of aldoxorubicin-treated patients, data from both the Phase II and III studies indicated a favorable cardiotoxicity profile vs doxorubicin. Despite the negative results from this Phase III study, the importance of anthracycline therapy in sarcoma management merits further investigation of the potential role of aldoxorubicin in this indication. Other avenues for progress include identification of sensitive histologies and biomarkers of activity, exploration of clinical niches without proven standard therapies, and exploration of alternate dosing strategies.

Aldoxorubicin therapy for the treatment of patients with advanced soft tissue sarcoma

Soft tissue sarcomas are a group of rare tumors of mesenchymal origin, and account for less than 1% of all cancers. The most commonly used drug for the treatment of soft tissue sarcoma is anthracycline chemotherapeutic agent, doxorubicin. The major limitation for doxorubicin is cardiotoxicity. Hence, to overcome this limitation and to increase efficacy, aldoxorubicin was developed, which has demonstrated activity in soft tissue sarcomas without much cardiotoxicity. In this review article, we discuss mechanism of action, pharmacokinetics, preclinical studies, clinical trial data and safety profile of aldoxorubicin and its potential applicability in the future of sarcoma treatment.

Display of the Albumin-Binding Domain in the Envelope Improves Lentiviral Vector Bioavailability

Vesicular stomatitis virus G glycoprotein (VSVg) is extensively used for retroviral and lentiviral vector (LV) pseudotyping. However, VSVg pseudotyped vectors are serum inactivated, blocking the in vivo gene delivery. Several strategies have been employed to prevent complement inactivation, including chemical and genetic envelope modifications. This study employed the streptococcal albumin-binding domain (ABD) to generate a construct to express ABD as a glycosylphosphatidylinositol-anchored protein. LV particles bearing ABD are able to bind bovine and human serum albumin in vitro. Neither the lentiviral vector production titer nor the in vitro transduction was affected by the ABD display. The study demonstrated that ABD-bearing LVs are protected from human complement inactivation. More importantly, intravenous administration demonstrated that the presence of ABD significantly reduces lentivector sequestration in liver and bone-marrow cells. Therefore, the use of ABD represents an improvement for in vivo gene therapy applications. The results strongly point to ABD display as a universal strategy to increase the in vivo efficacy of different viral vectors.

Aldoxorubicin: a tumor-targeted doxorubicin conjugate for relapsed or refractory soft tissue sarcomas

Despite available therapies after initial systemic therapy, prognosis remains poor in relapsed or refractory soft tissue sarcomas (STS). The rational and clinical development of novel agents to improve outcomes in this area of high unmet need is desperately warranted. Aldoxorubicin is a prodrug of doxorubicin that binds to serum albumin immediately after administration through an acid-sensitive hydrazone linker and is subsequently transported to tumor tissues where the acidic environment cleaves the linker and facilitates delivery of a tumor-targeted drug payload. In clinical studies to date, there has been evidence of efficacy and mitigated cardiac toxicity. In this review, we comprehensively detail the clinical development of aldoxorubicin in STS to date. Specifically, we highlight available data on the pharmacokinetics and efficacy from Phase I, Phase II, and Phase III trials in advanced or metastatic STS. We conclude with considerations for future directions of investigation for this promising antitumor agent.

A novel individual-cell-based mathematical model based on multicellular tumour spheroids for evaluating doxorubicin-related delivery in avascular regions

BACKGROUND AND PURPOSE

Effective drug delivery in the avascular regions of tumours, which is crucial for the promising antitumour activity of doxorubicin-related therapy, is governed by two inseparable processes: intercellular diffusion and intracellular retention. To accurately evaluate doxorubicin-related delivery in the avascular regions, these two processes should be assessed together. Here we describe a new approach to such an assessment.

EXPERIMENTAL APPROACH

An individual-cell-based mathematical model based on multicellular tumour spheroids was developed that describes the different intercellular diffusion and intracellular retention kinetics of doxorubicin in each cell layer. The different effects of a P-glycoprotein inhibitor (LY335979) and a hypoxia inhibitor (YC-1) were quantitatively evaluated and compared, in vitro (tumour spheroids) and in vivo (HepG2 tumours in mice). This approach was further tested by evaluating in these models, an experimental doxorubicin derivative, INNO 206, which is in Phase II clinical trials.

KEY RESULTS

Inhomogeneous, hypoxia-induced, P-glycoprotein expression compromised active transport of doxorubicin in the central area, that is, far from the vasculature. LY335979 inhibited efflux due to P-glycoprotein but limited levels of doxorubicin outside the inner cells, whereas YC-1 co-administration specifically increased doxorubicin accumulation in the inner cells without affecting the extracellular levels. INNO 206 exhibited a more effective distribution profile than doxorubicin.

CONCLUSIONS AND IMPLICATIONS

The individual-cell-based mathematical model accurately evaluated and predicted doxorubicin-related delivery and regulation in the avascular regions of tumours. The described framework provides a mechanistic basis for the proper development of doxorubicin-related drug co-administration profiles and nanoparticle development and could avoid unnecessary clinical trials.

Systemic Therapy for Advanced Soft Tissue Sarcoma

Soft tissue sarcomas are rare tumors that present with distant metastasis in up to 10% of patients. Survival has improved significantly because of advancements in histologic classification and improved management approaches. Older agents such as doxorubicin, ifosfamide, gemcitabine, and paclitaxel continue to demonstrate objective response rates from 18% to 25%. Newer agents such as trabectedin, eribulin, aldoxorubicin, and olaratumab have demonstrated improvements in progression-free survival, overall survival, or toxicity profiles. Future studies on treatment of advanced soft tissue sarcoma will continue to concentrate on reducing toxicity, personalization of therapy, and targeting novel pathways.

Albumin-Oxanorbornadiene Conjugates Formed ex Vivo for the Extended Circulation of Hydrophilic Cargo

Oxanorbornadiene dicarboxylate (OND) reagents were explored for the purpose of binding and releasing chemical cargos from endogenous circulating serum albumins. ONDs bearing gadolinium chelates as model cargos exhibited variable conjugation efficiencies with albumin in rat subjects that are consistent with the observed reactivity of each linker and their observed stability toward serum hydrolases in vitro. The terminal elimination rate from circulation was dependent on the identity of the OND used, and increased circulation time of gadolinium cargo was achieved for linkers bearing electrophilic fragments designed to react with cysteine-34 of circulating serum albumin. This binding of and release from endogenous albumin highlights the potential of OND linkers in the context of optimizing the pharmacokinetic parameters of drugs or diagnostic agents.

Update on clinical research and state of the art management of patients with advanced sarcomas and GIST

Sarcomas constitute a rare group of malignancies. According to histology, different treatment options are effective. For gastrointestinal stromal tumours (GISTs), targeted treatment with imatinib controls about 20% of advanced or metastatic disease, whereas chemotherapy is more effective for the rest of the sarcomas. Currently, new targeted treatments are emerging, showing activity in cases resistant to established primary treatment. On the other hand, the exciting results of immunotherapy for other solid tumours, for example, melanoma and lung cancer, make it a promising option in the fight against sarcomas. In this review, we have collected data of established and promising treatments in trials with a view to facilitating the sequencing of sarcoma treatments and for identifying the future of these therapeutic options.

Histology-Driven Therapy

Soft tissue tumors (STTs) are rare mesenchymal neoplasms accounting for less than 1% of adult cancers. More than 50 different subtypes of STTs have been identified, with this number expected to grow as our understanding of the complex genetic landscape of these diseases improves. As the classification of soft tissue neoplasms continues to diversify, so does the approach to therapy. Accurate histopathologic diagnosis, utilizing the appropriate ancillary immunohistochemical and molecular diagnostic platforms, underpins the oncologic management of soft tissue sarcomas. As increasing numbers of reproducible genetic abnormalities in soft tissue neoplasms are defined, molecular genetic and molecular cytogenetic investigations have become a standard part of the ancillary diagnostic repertoire. However, other soft tissue neoplasms lack reproducible genetic abnormalities, and for these, traditional histology and immunohistochemistry remain the cornerstones for diagnosis. Here, we give an overview of histology-driven therapy in STTs, highlighting the critical role of accurate surgical pathology in guiding the systemic treatment of patients with these neoplasms, and the importance of close collaboration between the surgical pathologist and the oncologist. We also summarize what is considered standard practice in nonhistology- and histology-driven therapy.

Current and advancing systemic treatment options for soft tissue sarcomas

INTRODUCTION

Soft tissue sarcomas are a collection of rare malignancies, the treatment of which has evolved over time. Although cytotoxic chemotherapy remains the cornerstone of management of metastatic disease, many new treatments have been developed or show great promise in the treatment of soft tissue sarcoma. Research into the different underlying pathogenesis of individual subtypes has driven progress in treatment. This has allowed development of treatments targeted to specific subtypes of sarcoma.

AREAS COVERED

We provide a review of the current field of systemic therapy in soft tissue sarcoma. This is followed by an in-depth analysis of recent developments in treatment, as well as new treatments that are aimed at specific subtypes of sarcoma, and the biological rationale behind these therapies. We also look in detail at the promising new agents currently in development.

EXPERT OPINION

Much progression has been made in treatment of soft tissue sarcomas with multiple exciting new treatments in development. However outcomes in general remain poor. Further research into the underlying pathogenesis of soft tissue sarcomas may help deliver more effective systemic therapies. Increased collaboration between basic science, translational and clinical investigators is required at national and international levels to maximise progress.

Phase I and pharmacokinetic study of the novel anthracycline derivative 5-imino-13-deoxydoxorubicin (GPX-150) in patients with advanced solid tumors

PURPOSE

5-imino-13-deoxydoxorubicin (DIDOX; GPX-150) is a doxorubicin analog modified in two locations to prevent formation of cardiotoxic metabolites and reactive oxygen species. Preclinical studies have demonstrated anti-cancer activity without cardiotoxicity. A phase I study was performed in order to determine the maximum-tolerated dose (MTD) of GPX-150 in patients with metastatic solid tumors.

METHODS

GPX-150 was administered as an intravenous infusion every 21 days for up to 8 cycles. An accelerated dose escalation was used for the first three treatment groups. The dosing groups were (A) 14 mg/m(2), (B) 28 mg/m(2), (C), 56 mg/m(2), (D) 84 mg/m(2), (E) 112 mg/m(2), (F) 150 mg/m(2), (G) 200 mg/m(2), and (H) 265 mg/m(2). Pharmacokinetic samples were drawn during the first 72 h of cycle 1.

RESULTS

The MTD was considered to be reached at the highest dosing level of 265 mg/m(2) since dose reduction was required in 5 of 6 patients for neutropenia. The most frequent adverse events were neutropenia, anemia, fatigue, and nausea. No patients experienced cardiotoxicity while on the study. The best overall response was stable disease in four (20 %) patients. Pharmacokinetic analysis revealed an AUC of 8.0 (±2.6) μg · h/mL, a clearance of 607 (±210) mL/min/m(2) and a t1/2β of 13.8 (±4.6) hours.

CONCLUSIONS

GPX-150 administered every 21 days has an acceptable side effect profile and no cardiotoxicity was observed. Further investigation is needed to determine the efficacy of GPX-150 in anthracycline-sensitive malignancies.