Early-drug development in the era of immuno-oncology: are we ready to face the challenges?

Analysis of off-tumour toxicities of T-cell-engaging bispecific antibodies via donor-matched intestinal organoids and tumouroids

Predicting the toxicity of cancer immunotherapies preclinically is challenging because models of tumours and healthy organs do not typically fully recapitulate the expression of relevant human antigens. Here we show that patient-derived intestinal organoids and tumouroids supplemented with immune cells can be used to study the on-target off-tumour toxicities of T-cell-engaging bispecific antibodies (TCBs), and to capture clinical toxicities not predicted by conventional tissue-based models as well as inter-patient variabilities in TCB responses. We analysed the mechanisms of T-cell-mediated damage of neoplastic and donor-matched healthy epithelia at a single-cell resolution using multiplexed immunofluorescence. We found that TCBs that target the epithelial cell-adhesion molecule led to apoptosis in healthy organoids in accordance with clinical observations, and that apoptosis is associated with T-cell activation, cytokine release and intra-epithelial T-cell infiltration. Conversely, tumour organoids were more resistant to damage, probably owing to a reduced efficiency of T-cell infiltration within the epithelium. Patient-derived intestinal organoids can aid the study of immune-epithelial interactions as well as the preclinical and clinical development of cancer immunotherapies.

When Less May Be Enough: Dose Selection Strategies for Immune Checkpoint Inhibitors Focusing on AntiPD-(L)1 Agents

Early clinical trials investigating antiPD(L)-1 agents rarely reached a maximum tolerated dose (MTD), and efficacy signals were observed even at the lowest dose levels. Most extended treatment intervals investigated indicated that these drugs do not follow a direct dose-toxicity or dose-efficacy relationship. Within this context and considering the high cost of antiPD(L)-1 agents, there is a significant debate on whether lower doses or the administration of such agents at an extended interval should be prospectively evaluated in already-approved agents, or at least be considered in novel combination trials involving antiPD(L)-1 drugs. Herein, we review the dosing, overall response rates, and incidence of treatment-related adverse events of antiPD(L)-1 agents in early dose-escalation trials and discuss the appropriateness of recommended Phase 2 dose selection as well as the final regulatory approved doses of such agents. Efficacy and safety data from randomized dose-range Phase 2 trials and real-world data (RWD) on the usage of lower doses and/or non-standard extended treatment intervals are also examined. As the accumulating evidence suggests lower doses or extended dosing intervals of antiPD(L)-1 may achieve a similar clinical benefit in comparison to the currently approved doses, we address the clinical and financial toxicity implications of using potentially higher doses than necessary. Last, we discuss ways to resolve the current dosing conundrum of antiPD-(L)1 agents such as performing near-equivalence studies and propose a framework for future development of immunotherapeutics to find the lowest efficacious dose instead of MTD.

Contemporary dose-escalation methods for early phase studies in the immunotherapeutics era

Phase 1 dose-escalation trials are crucial to drug development by providing a framework to assess the toxicity of novel agents in a stepwise and monitored fashion. Despite widely adopted, rule-based dose-escalation methods (such as 3 + 3) are limited in finding the maximum tolerated dose (MTD) and tend to treat a significant number of patients at subtherapeutic doses. Newer methods of dose escalation, such as model-based and model-assisted designs, have emerged and are more accurate in finding MTD. However, these designs have not yet been broadly embraced by investigators. In this review, we summarise the advantages and disadvantages of contemporary dose-escalation methods, with emphasis on model-assisted designs, including time-to-event designs and hybrid methods involving optimal biological dose (OBD). The methods reviewed include mTPI, keyboard, BOIN, and their variations. In addition, the challenges of drug development (and dose-escalation) in the era of immunotherapeutics are discussed, where many of these agents typically have a wide therapeutic window. Fictional examples of how the dose-escalation method chosen can alter the outcomes of a phase 1 study are described, including the number of patients enrolled, the trial's timeframe, and the dose level chosen as MTD. Finally, the recent trends in dose-escalation methods applied in phase 1 trials in the immunotherapeutics era are reviewed. Among 856 phase I trials from 2014 to 2019, a trend towards the increased use of model-based and model-assisted designs over time (OR = 1.24) was detected. However, only 8% of the studies used non-rule-based dose-escalation methods. Increasing familiarity with such dose-escalation methods will likely facilitate their uptake in clinical trials.