The development of phase I cancer trial methodologies: the use of pharmacokinetic and pharmacodynamic end points sets the scene for phase 0 cancer clinical trials

Are we providing best-available care to newly diagnosed glioblastoma patients? Systematic review of phase III trials in newly diagnosed glioblastoma 2005-2022

Background

Glioblastoma is the most aggressive primary brain cancer with a poor prognosis. Despite numerous studies in the past 17 years, effective treatment options for glioblastoma remain limited. In this study, we aimed to identify and compare phase III clinical trials for glioblastoma in terms of efficacy and baseline characteristics.

Methods

A systematic literature search was conducted using PubMed and ClinicalTrials.gov to identify phase III clinical trials for glioblastoma in adult patients. The target population included adult patients aged 18 years and above (younger cohort) and patients ≥60 years of age (elderly cohort). The search results were screened based on predefined inclusion criteria, and the included trials were analyzed for their study design, baseline characteristics, and survival results.

Results

Eleven trials met the inclusion criteria in the younger cohort. Of these, three reported a statistically significant improvement in overall survival (OS), including the EORTC/NCIC study (NCT00006353), EF-14 (NCT00916409), and CeTeG (NCT01149109). Of the 11 trials, eight were open-label randomized trials, including all of the positive ones, while three negative trials employed treatment blinding and a placebo control. The baseline characteristics of the trials [such as extent of resection, age, gender, and O(6)-methylguanine-DNA-methyltransferase (MGMT) promoter methylation status] did not significantly differ between positive and negative trials. Isocitrate dehydrogenase (IDH) mutation status was analyzed in only two trials, with a small percentage of IDH-mutated tumors in each. Additionally, three more trials in the elderly cohort showed a statistically significant improvement of OS, the NOA-08 trial, the ISRCTN81470623-trial by Malmström et al. and NCT00482677-trial by Perry et al. Their baseline characteristics and implications are also analyzed.

Conclusion

This analysis of phase III clinical trials for glioblastoma conducted since 2005 showed that the majority of trials did not result in a significant improvement in OS. Among the trials included in this analysis, only the EORTC/NCIC, EF-14, and CeTeG studies demonstrated a positive OS outcome in the younger cohort.

Phase 0 and window of opportunity clinical trial design in neuro-oncology: a RANO review

Glioblastoma is a devastating disease with poor prognosis. Few effective chemotherapeutics are currently available, and much effort has been expended to identify new drugs capable of slowing tumor progression. The phase 0 trial design was developed to facilitate early identification of promising agents for cancer that should undergo accelerated approval. This design features an early in-human study that enrolls a small number of patients who receive subtherapeutic doses of medication with the goals of describing pharmacokinetics through drug blood level measurements and determining intratumoral concentrations of the investigational compound as well as pharmacodynamics by studying the biochemical and physiological effects of drugs. In neuro-oncology, however, the presence of the blood-brain barrier and difficulty in obtaining brain tumor tissue warrant a separate set of considerations. In this paper, we critically reviewed the protocols used in all brain tumor related in-human phase 0 and phase 0-like ("window of opportunity") studies between 1993 and 2018, as well as ongoing clinical trials, and identified major challenges in trial design as applied to central nervous system tumors that include surgical specimen collection and storage, brain tumor drug level analysis, and confirmation of drug action. We therefore propose that phase 0 trials in neuro-oncology should include (i) only patients in whom a resection of the tumor is planned, (ii) use of clinical doses of an investigational agent, (iii) tissue sampling from enhancing and non-enhancing portions of the tumor, and (iv) assessment of drug-specific target effects. Standardization of clinical protocols for phase 0/window of opportunity studies can help accelerate the development of effective treatments for glioblastoma.

Embracing model-based designs for dose-finding trials

BACKGROUND

Dose-finding trials are essential to drug development as they establish recommended doses for later-phase testing. We aim to motivate wider use of model-based designs for dose finding, such as the continual reassessment method (CRM).

METHODS

We carried out a literature review of dose-finding designs and conducted a survey to identify perceived barriers to their implementation.

RESULTS

We describe the benefits of model-based designs (flexibility, superior operating characteristics, extended scope), their current uptake, and existing resources. The most prominent barriers to implementation of a model-based design were lack of suitable training, chief investigators' preference for algorithm-based designs (e.g., 3+3), and limited resources for study design before funding. We use a real-world example to illustrate how these barriers can be overcome.

CONCLUSIONS

There is overwhelming evidence for the benefits of CRM. Many leading pharmaceutical companies routinely implement model-based designs. Our analysis identified barriers for academic statisticians and clinical academics in mirroring the progress industry has made in trial design. Unified support from funders, regulators, and journal editors could result in more accurate doses for later-phase testing, and increase the efficiency and success of clinical drug development. We give recommendations for increasing the uptake of model-based designs for dose-finding trials in academia.

FGFR-TACC gene fusions in human glioma

Chromosomal translocations joining in-frame members of the fibroblast growth factor receptor-transforming acidic coiled-coil gene families (the FGFR-TACC gene fusions) were first discovered in human glioblastoma multiforme (GBM) and later in many other cancer types. Here, we review this rapidly expanding field of research and discuss the unique biological and clinical features conferred to isocitrate dehydrogenase wild-type glioma cells by FGFR-TACC fusions. FGFR-TACC fusions generate powerful oncogenes that combine growth-promoting effects with aneuploidy through the activation of as yet unclear intracellular signaling mechanisms. FGFR-TACC fusions appear to be clonal tumor-initiating events that confer strong sensitivity to FGFR tyrosine kinase inhibitors. Screening assays have recently been reported for the accurate identification of FGFR-TACC fusion variants in human cancer, and early clinical data have shown promising effects in cancer patients harboring FGFR-TACC fusions and treated with FGFR inhibitors. Thus, FGFR-TACC gene fusions provide a "low-hanging fruit" model for the validation of precision medicine paradigms in human GBM.

Pharmacodynamic endpoints as clinical trial objectives to answer important questions in oncology drug development

Analyzing the molecular interplay between malignancies and therapeutic agents is rarely a straightforward process, but we hope that this special issue of Seminars has highlighted the clinical value of such endeavors as well as the relevant theoretical and practical considerations. Here, we conclude with both an overview of the various high-value applications of clinical pharmacodynamics (PD) in developmental therapeutics and an outline of the framework for incorporating PD analyses into the design of clinical trials. Given the increasingly recognized importance of determining and administering the biologically effective dose (BED) and schedule of targeted agents, we explain how clinical PD biomarkers specific to the agent mechanism of action (MOA) can be used for the development of pharmacodynamics-guided biologically effective dosage regimens (PD-BEDR) to maximize the efficacy and minimize the toxicity of targeted therapies. In addition, we discuss how MOA-based PD biomarker analyses can be used both as patient selection diagnostic tools and for designing novel drug combinations targeting the specific mutational signature of a given malignancy. We also describe the role of PD analyses in clinical trials, including for MOA confirmation and dosage regimen optimization during phase 0 trials as well as for correlating molecular changes with clinical efficacy when establishing proof-of-concept in phase I/II trials. Finally, we outline the critical technological developments that are needed to enhance the quality and quantity of future clinical PD data collection, broaden the types of molecular questions that can be answered in the clinic, and, ultimately, improve patient outcomes.

The histone methyltransferase SMYD2 methylates PARP1 and promotes poly(ADP-ribosyl)ation activity in cancer cells

Poly(ADP-ribose) polymerase-1 (PARP1) catalyzes the poly(ADP-ribosyl)ation of protein acceptors using NAD(+) as the substrate is now considered as an important target for development of anticancer therapy. PARP1 is known to be post-translationally modified in various ways including phosphorylation and ubiquitination, but the physiological role of PARP1 methylation is not well understood. Herein we demonstrated that the histone methyltransferase SMYD2, which plays critical roles in human carcinogenesis, mono-methylated PARP1. We confirmed lysine 528 to be a target of SMYD2-dependent PARP1 methylation by LC-MS/MS and Edman Degradation analyses. Importantly, methylated PARP1 revealed enhanced poly(ADP-ribose) formation after oxidative stress, and positively regulated the poly(ADP-ribosyl)ation activity of PARP1. Hence, our study unveils a novel mechanism of PARP1 in human cancer through its methylation by SMYD2.

Application of hematological toxicity modeling in clinical development of abexinostat (S-78454, PCI-24781), a new histone deacetylase inhibitor

PURPOSE

A population pharmacokinetic/pharmacodynamic (PK/PD) model was developed to describe the thrombocytopenia (dose-limiting toxicity) of abexinostat, a new histone deacetylase inhibitor. An optimal administration schedule of the drug was determined using a simulation-based approach.

METHODS

Early PK and PK/PD data were analysed using a sequential population modeling approach (NONMEM 7), allowing for the description of a PK profile and platelet-count decrease after abexinostat administration with various administration schedules. Simulations of platelet count with several administration schedules over 3-week treatment cycles (ASC) and over a day (ASD) were computed to define the optimal schedule that limits the depth of thrombocytopenia.

RESULTS

An intermediate PK/PD model accurately described the data. The administration of abexinostat during the first 4 days of each week in a 3-week cycle resulted in fewer adverse events (with no influence of ASD on platelet count profiles), and corresponded to the optimal treatment schedule. This administration schedule was clinically evaluated in a phase I clinical trial and allowed for the definition of a new maximum tolerated dose (MTD), leading to a nearly 30% higher dose-intensity than that of another previously tested schedule. Lastly, a final model was built using all of the available data.

CONCLUSIONS

The final model, characterizing the dose-effect and the dose-toxicity relationships, provides a useful modeling tool for clinical drug development.

Microdosing and drug development: past, present and future

INTRODUCTION

Microdosing is an approach to early drug development where exploratory pharmacokinetic data are acquired in humans using inherently safe sub-pharmacologic doses of drug. The first publication of microdose data was 10 years ago and this review comprehensively explores the microdose concept from conception, over the past decade, up until the current date.

AREAS COVERED

The authors define and distinguish the concept of microdosing from similar approaches. The authors review the ability of microdosing to provide exploratory pharmacokinetics (concentration-time data) but exclude microdosing using positron emission tomography. The article provides a comprehensive review of data within the peer-reviewed literature as well as the latest applications and a look into the future, towards where microdosing may be headed.

EXPERT OPINION

Evidence so far suggests that microdosing may be a better predictive tool of human pharmacokinetics than alternative methods and combination with physiologically based modelling may lead to much more reliable predictions in the future. The concept has also been applied to drug-drug interactions, polymorphism and assessing drug concentrations over time at its site of action. Microdosing may yet have more to offer in unanticipated directions and provide benefits that have not been fully realised to date.

Principles of dose finding studies in cancer: a comparison of trial designs

PURPOSE

One key aim of Phase I cancer studies is to identify the dose of a treatment to be further evaluated in Phase II. We describe, in non-statistical language, three classes of dose-escalation trial design and compare their properties.

METHODS

We review three classes of dose-escalation design suitable for Phase I cancer trials: algorithmic approaches (including the popular 3 + 3 design), Bayesian model-based designs and Bayesian curve-free methods. We describe an example from each class and summarize the advantages and disadvantages of the design classes.

RESULTS

The main benefit of algorithmic approaches is the simplicity with which they may be communicated: it may be for this reason alone that they are still employed in the vast majority of Phase I trials. Model-based and curve-free Bayesian approaches are preferable to algorithmic methods due to their superior ability to identify the dose with the desired toxicity rate and their allocation of a greater proportion of patients to doses at, or close to, that dose.

CONCLUSIONS

For statistical and practical reasons, algorithmic methods cannot be recommended. The choice between a Bayesian model-based or curve-free approach depends on the previous information available about the compound under investigation. If this provides assurance about a particular model form, the model-based approach would be appropriate; if not, the curve-free method would be preferable.

Phase 0 clinical trials in oncology new drug development

Research focus of pharmaceutical industry has expanded to a larger extent in last few decades putting many more new molecules, particularly targeted agents, for the clinical development. On the other hand, researchers are facing serious challenges due to high failure rates of new molecules in clinical studies. The United States Food and Drug Administration (FDA) in combination with academia and industry experts identified many factors responsible for failures of new molecules, and with a vision of taking traditional drug development model toward an innovative paradigm shift, issued regulatory guidance on conduct of exploratory investigational new drug (exploratory IND) studies, often called as phase 0 clinical trials, requiring reduced preclinical testing, which has special relevance to life-threatening diseases such as cancer. Phase 0 trials, utilizing much lower drug doses, provide an opportunity to explore the clinical behavior of new molecules very early in the drug development pathway, helping to identify the promising candidates and eliminating non-promising molecules, thus improving the efficiency of overall drug development with significant savings of resources. Being non-therapeutic in nature, these studies, however, pose certain ethical challenges requiring careful study designing and informed consent process. This article reviews the insights and perspectives for the feasibility, utility, planning, designing and conduct of phase 0 clinical trials, in addition to ethical issues and industrial perspective focused at oncology new drug development.

What are the endpoints of therapy for acute leukemias? Old definitions and new challenges

Acute leukemias are complex diseases on multiple levels, and laboratory efforts over the past 3 decades have focused on better understanding of the molecular underpinnings and their stem cell biology. We now have a panoply of technologic advances that allow us to characterize individual leukemias by molecular profiles that relate directly to clinical behavior, to detect minimal residual disease, and to begin to develop "targeted" therapeutic strategies based on molecular considerations. There are a number of challenges surrounding this task: first, how to combine these agents with traditional chemotherapeutics and/or with each other to maximize leukemic cell kill and increase the cure rate; second, how to use these targeted agents in the minimal residual disease with potential curative intent; third, for patients unable to tolerate or unlikely to benefit from aggressive approaches, how to use one or more of these agents to reduce tumor bulk and either permit some restoration of normal marrow function or induce morphologic and functional differentiation of the leukemic clone to overcome the leukemia-associated bone marrow failure; and lastly, how to measure the effects of these agents on the molecular and cellular biologic levels in ways that correlate with and might even predict overall clinical outcome. These challenges are further complicated by the inherent heterogeneity in host biology; disease etiology and biology; and interactions among host, disease, and treatment that ultimately determine individual clinical outcomes. Toward this end, we will discuss selected issues surrounding new clinical trial designs and the development of clinically relevant molecular endpoints that might facilitate the development of new treatment approaches that will improve the outlook for adults with acute leukemias.

Role of Phase 0 trials in drug development

Phase 0 trials can provide proof of concept that an agent modulates its intended target without exposing patients to the drug-tolerability testing that precedes efficacy evaluation. Drugs that do not modulate their targets can be discarded, focusing development resources on the most clinically promising agents. However, wider uptake of Phase 0 trials may be hindered by ethical concerns over their lack of therapeutic intent, the substantial resources required to develop and validate target assays or skepticism that such trials save development time.

Understanding DNA damage response and DNA repair pathways: applications to more targeted cancer therapeutics

Radiation therapy and many of the commonly used cancer chemotherapeutic drugs target DNA for cytotoxicity. Indeed, the subsequent DNA damage response (DDR) to these cancer treatments in both malignant and normal cells/tissues determines the therapeutic index (TI) of the treatment. The DDR is a complex set of cell processes involving multiple DNA repair, cell cycle regulation, and cell death/survival pathways (or networks) with both damage specificity and coordination of the DDR to different types of DNA damage. Over the last decade, significant progress has been made in elucidating these complex cellular and molecular networks involved in the DDR in human tumor and normal tissues. Based on what has been learned about these processes using experimental in vitro and in vivo models, DDR and DNA pathways are now potential targets for cancer therapy. This article presents an overview of our current understanding of the DDR, including the key DNA repair pathways involved in determining the cytotoxicity to several classes of chemotherapy drugs (CT) as well as ionizing radiation (IR). Since many different types of human cancers can arise from genetic or epigenetic changes in the DDR and DNA repair pathways, this article also covers recent developments in cancer therapeutics that attempt to target these specific tumor-related DDR/DNA repair defects as monotherapy or, more commonly, when combined with conventional cancer treatments.

Leveraging exploratory investigational new drug studies to accelerate drug development

In 2006, the U.S. Food and Drug Administration published its guide on exploratory investigational new drug (IND) studies with the goal of making the approach to early-stage, pilot clinical trials more flexible within the context of current regulations. The exploratory IND allows sponsors to initiate clinical trials of limited scale with reduced preclinical requirements. These studies may be important vehicles for the conduct of proof-of-principle pharmacodynamic investigations of highly potent molecules, for bioavailability studies that require only a single drug dose to be administered, and for imaging trials that permit critical dosimetry and biodistribution investigations of new molecules. These trials were done with no therapeutic intent and must be followed by traditional dose-escalation investigations that are supported by standard preclinical toxicologic and pharmacologic studies. To the extent that they allow early evaluations of essential drug characteristics that can only be obtained in humans, exploratory IND trials have the potential to limit the cost and improve the development times of new agents.

The ethics of phase 0 oncology trials

Recent guidance from the Food and Drug Administration supports the conduct of a new type of exploratory clinical trial, commonly called phase 0 clinical trials. Proponents argue that phase 0 clinical trials have the potential to expedite the development of new oncology drugs while exposing fewer research subjects to the risks of experimental treatments. At the same time, phase 0 oncology trials raise important ethical concerns that have received little attention. In particular, there is a question of whether it is ethical to enroll individuals in research that offers them no potential for clinical benefit. Further concern focuses on the inclusion of terminally ill and consequently vulnerable cancer patients in these trials. To evaluate these concerns, this article considers relevant empirical data from phase 1 oncology trials and develops several recommendations regarding the conduct of phase 0 clinical trials in oncology.

Oncologic phase 0 trials incorporating clinical pharmacodynamics: from concept to patient

The U.S. Food and Drug Administration recently issued an Exploratory Investigational New Drug (IND) guidance that provides a platform for the evaluation of targeted anticancer agents in small, early-phase human clinical trials that can be used to establish the feasibility of proof-of-principle target modulation assays, as well as the preliminary pharmacokinetics and molecular imaging potential of new anticancer molecules. The exploratory IND allows for reduced requirements for manufacturing and toxicologic assessment. Early clinical trials done in this fashion have no therapeutic intent. In this series of articles in CCR Focus, the development of this new IND mechanism, its effect on clinical trial design and clinical pharmacodynamics, the ethical implications of nontherapeutic clinical investigations, and the perspective of the pharmaceutical industry on this approach are examined.

Designing phase 0 cancer clinical trials

Phase 0 trials are designed primarily to evaluate the pharmacodynamic and/or pharmacokinetic properties of selected investigational agents before initiating more traditional phase I testing. One of the major objectives of phase 0 trials is to interrogate and refine a target or biomarker assay for drug effect in human samples implementing procedures developed and validated in preclinical models. Thus, close collaboration between laboratory scientists and clinical investigators is essential to the design and conduct of phase 0 trials. Given the relatively small number of patients and tissue samples, showing a significant drug effect in phase 0 trials requires precise and reproducible assay procedures and innovative statistical methodology. Furthermore, phase 0 trials involving limited exposure of a study agent administered at low doses and/or for a short period allow them to be initiated under the Food and Drug Administration exploratory investigational new drug guidance with less preclinical toxicity data than usually required for traditional first-in-human studies. Because of the very limited drug exposure, phase 0 trials offer no chance of therapeutic benefit, which can impede patient enrollment, particularly if invasive tumor biopsies are required. The challenges to accrual are not insurmountable, however, and well-designed and executed phase 0 trials are feasible and have great potential for improving the efficiency and success of subsequent trials, particularly those evaluating molecularly targeted agents.