Opportunities for using in silico-based extended dosing regimens for monoclonal antibody immune checkpoint inhibitors

High-throughput, low-cost quantification of 11 therapeutic antibodies using caprylic acid precipitation and LC-MS/MS

BACKGROUND

Therapeutic drug monitoring of treatment with therapeutic antibodies is hampered by the application of a wide range of different methods in the quantification of serum levels. LC-MS based methods could significantly improve comparability of results from different laboratories, but such methods are often considered complicated and costly. We developed a method for LC-MS/MS based quantification of 11 therapeutic antibodies concomitantly measured in a single run, with emphasis on simplicity in sample preparation and low cost.

RESULTS

After a single-step sample purification using caprylic acid precipitation to remove interfering proteins, the sample underwent proteolysis followed by LC-MS/MS analysis. Infliximab is used as internal standard for sample preparation while isotope-labeled signature peptides identified for each analyte are internal standards for the LC-MS/MS normalization. The method was validated according to recognized guidelines, and pipetting steps can be performed by automated liquid handling systems. The total precision of the method ranged between 2.7 and 7.3 % (5.1 % average) across the quantification range of 4-256 μg/ml for all 11 drugs, with an average accuracy of 96.3 %. Matrix effects were xamined in 55 individual patient samples instead of the recommended 6, and 147 individual patient samples were screened for interfering compounds.

SIGNIFICANCE AND NOVELTY

Our method for simultaneous quantification of 11 t-mAb in human serum allows an unprecedented integration of robustness, speed and reduced complexity, which could pave the way for uniform use in research projects and clinical settings alike. In addition, the first LC-MS protocol for signature peptide-based quantification of durvalumab is described. This high throughput method can be readily adapted to a drug panel of choice.

Optimizing the doses of cancer drugs after usual dose finding

Since the middle of the 20th century, oncology's dose-finding paradigm has been oriented toward identifying a drug's maximum tolerated dose, which is then carried forward into phase 2 and 3 trials and clinical practice. For most modern precision medicines, however, maximum tolerated dose is far greater than the minimum dose needed to achieve maximal benefit, leading to unnecessary side effects. Regulatory change may decrease maximum tolerated dose's predominance by enforcing dose optimization of new drugs. Dozens of already approved cancer drugs require re-evaluation, however, introducing a new methodologic and ethical challenge in cancer clinical trials. In this article, we assess the history and current landscape of cancer drug dose finding. We provide a set of strategic priorities for postapproval dose optimization trials of the future. We discuss ethical considerations for postapproval dose optimization trial design and review three major design strategies for these unique trials that would both adhere to ethical standards and benefit patients and funders. We close with a discussion of financial and reporting considerations in the realm of dose optimization. Taken together, we provide a comprehensive, bird's eye view of the postapproval dose optimization trial landscape and offer our thoughts on the next steps required of methodologies and regulatory and funding regimes.

High-Throughput Antigen Microarray Identifies Longitudinal Prognostic Autoantibody for Chemoimmunotherapy in Advanced Non-Small Cell Lung Cancer

Chemoimmunotherapy has evolved as a standard treatment for advanced non-small cell lung cancer (aNSCLC). However, inevitable drug resistance has limited its efficacy, highlighting the urgent need for biomarkers of chemoimmunotherapy. A three-phase strategy to discover, verify, and validate longitudinal predictive autoantibodies (AAbs) for aNSCLC before and after chemoimmunotherapy was employed. A total of 528 plasma samples from 267 aNSCLC patients before and after anti-PD1 immunotherapy were collected, plus 30 independent formalin-fixed paraffin-embedded samples. Candidate AAbs were firstly selected using a HuProt high-density microarray containing 21,000 proteins in the discovery phase, followed by validation using an aNSCLC-focused microarray. Longitudinal predictive AAbs were chosen for ELISA based on responders versus non-responders comparison and progression-free survival (PFS) survival analysis. Prognostic markers were also validated using immunohistochemistry and publicly available immunotherapy datasets. We identified and validated a panel of two AAbs (MAX and DHX29) as pre-treatment biomarkers and another panel of two AAbs (MAX and TAPBP) as on-treatment predictive markers in aNSCLC patients undergoing chemoimmunotherapy. All three AAbs exhibited a positive correlation with early responses and PFS (p < 0.05). The kinetics of MAX AAb showed an increasing trend in responders (p < 0.05) and a tendency to initially increase and then decrease in non-responders (p < 0.05). Importantly, MAX protein and mRNA levels effectively discriminated PFS (p < 0.05) in aNSCLC patients treated with immunotherapy. Our results present a longitudinal analysis of changes in prognostic AAbs in aNSCLC patients undergoing chemoimmunotherapy.

Killing a fly with a sledgehammer: Atezolizumab exposure in real-world lung cancer patients

Atezolizumab is an anti-PDL1 approved for treating lung cancer. A threshold of 6 μg/mL in plasma has been associated with target engagement. The extent to which patients could be overexposed with the standard 1200 mg q3w dosing remains unknown. Here, we monitored atezolizumab peak and trough levels in 27 real-world patients with lung cancer as part of routine therapeutic drug monitoring. Individual pharmacokinetic (PK) parameters were calculated using a population approach and optimal dosing-intervals were simulated with respect to the target trough levels. No patient had plasma levels below 6 μg/mL. The results showed that the mean trough level after the first treatment was 78.3 ± 17 μg/mL, that is, 13 times above the target concentration. The overall response rate was 55.5%. Low-grade immune-related adverse events was observed in 37% of patients. No relationship was found between exposure metrics of atezolizumab (i.e., minimum plasma concentration, maximum plasma concentration, and area under the curve) and pharmacodynamic end points (i.e., efficacy and toxicity). Further simulations suggest that the dosing interval could be extended from 21 days to 49 up to 136 days (mean: 85.7 days, i.e., q12w), while ensuring plasma levels still above the 6 μg/mL target threshold. This observational, real-world study suggests that the standard 1200 mg q3w fixed-dose regimen of atezolizumab results in significant overexposure in all the patients. This was not associated with increased side effects. As plasma levels largely exceed pharmacologically active concentrations, interindividual variability in PK parameters did not impact efficacy. Our data suggest that dosing intervals could be markedly extended with respect to the target threshold associated with efficacy.

Combining atezolizumab 1200 mg with bevacizumab 15 mg/kg: based on science or just revenues?

Dose optimisation is increasingly important in oncology, as exemplified by the US Food and Drug Administration's Project Optimus initiative, which is aligned with similar initiatives in other countries. In parallel, multiple stakeholders have raised concerns about anticancer drug prices, affordability, and access. This is of particular concern to government payers as well as patients and physicians in low- and middle-income countries. As anticancer drugs have historically been approved at the maximally tolerated dose, it is now highly relevant to question whether lower doses are equally effective and can be delivered at lower doses, resulting in less toxicity for patients, and lower costs for patients and payers. We illustrate this opportunity by discussing the combination of atezolizumab and bevacizumab, approved in multiple countries for both non-small cell lung cancer and hepatocellular cancer. Our conclusion is that the cost of this regimen can be reduced by more than 80%, an opportunity that should be considered by patients, prescribers, payers, and policymakers.

Interventional pharmacoeconomics for immune checkpoint inhibitors through alternative dosing strategies

Immune checkpoint inhibitors (ICIs) are approved for the treatment of a variety of cancer types. The doses of these drugs, though approved by the Food and Drug Administration (FDA), have never been optimised, likely leading to significantly higher doses than required for optimal efficacy. Dose optimisation would hypothetically decrease the risk, severity, and duration of immune-related adverse events, as well as provide an opportunity to reduce costs through interventional pharmacoeconomic strategies such as off-label dose reductions or less frequent dosing. We summarise existing evidence for ICI dose optimisation to advocate for the role of interventional pharmacoeconomics.

Adopting Weight-Based Dosing With Pharmacy-Level Stewardship Strategies Could Reduce Cancer Drug Spending By Millions

Immune checkpoint inhibitors, a class of drugs used in approximately forty unique cancer indications, are a sizable component of the economic burden of cancer care in the US. Instead of personalized weight-based dosing, immune checkpoint inhibitors are most commonly administered at "one-size-fits-all" flat doses that are higher than necessary for the vast majority of patients. We hypothesized that personalized weight-based dosing along with common stewardship efforts at the pharmacy level, such as dose rounding and vial sharing, would lead to reductions in immune checkpoint inhibitor use and lower spending. Using data from the Veterans Health Administration (VHA) and Medicare drug prices, we estimated reductions in immune checkpoint inhibitor use and spending that would be associated with pharmacy-level stewardship strategies, in a case-control simulation study of individual patient-level immune checkpoint inhibitor administration events. We identified baseline annual VHA spending for these drugs of approximately $537 million. Combining weight-based dosing, dose rounding, and pharmacy-level vial sharing would generate expected annual VHA health system savings of $74 million (13.7 percent). We conclude that adoption of pharmacologically justified immune checkpoint inhibitor stewardship measures would generate sizable reductions in spending for these drugs. Combining these operational innovations with value-based drug price negotiation enabled by recent policy changes may improve the long-term financial viability of cancer care in the US.

In Silico Re-Optimization of Atezolizumab Dosing Using Population Pharmacokinetic Simulation and Exposure-Response Simulation

Atezolizumab, a humanized monoclonal antibody against programmed cell death ligand 1 (PD-L1), was initially approved in 2016, around the same time that the sponsor published the minimum serum concentration to maintain the saturation of receptor occupancy (6 μg/mL). The initially approved dose regimen of 1200 mg every 3 weeks (q3w) was subsequently modified to 840 mg q2w or 1680 mg q4w through pharmacokinetic simulations. Yet, each standard regimen yields steady-state trough concentrations (CMIN,SS ) far exceeding (≈ 40-fold) the stated target concentration. Additionally, the steady-state area under the plasma drug concentration-time curve (AUCSS ) at 1200 mg q3w was significantly (P = .027) correlated with the probability of adverse events of special interest (AESIs) in patients with non-small cell lung cancer (NSCLC) and, coupled with excess exposure, this provides incentive to explore alternative dose regimens to lower the exposure burden while maintaining an effective CMIN,SS . In this study, we first identified 840 mg q6w as an extended-interval regimen that could robustly maintain a serum concentration of 6 μg/mL (≥99% of virtual patients simulated, n = 1000), then applied this regimen to an approach that administers 2 "loading doses" of standard-interval regimens for a future clinical trial aiming to personalize dose regimens. Each standard dose was simulated for 2 loading doses, then 840 mg q6w thereafter; all yielded cycle-7 CMIN,SS values of >6 μg/mL in >99% of virtual patients. Further, the AUCSS from 840 mg q6w resulted in a flattening (P = .63) of the exposure-response relationship with adverse events of special interest (AESIs). We next aim to verify this in a clinical trial seeking to validate extended-interval dosing in a personalized approach using therapeutic drug monitoring.

A non-inferiority randomized phase III trial of standard immunotherapy by checkpoint inhibitors vs. reduced dose intensity in responding patients with metastatic cancer: the MOIO protocol study

BACKGROUND

Immunotherapy (IO) has become a standard of care for treating various types of metastatic cancers and has significantly improved clinical outcome. With the exception of metastatic melanoma in complete response for which treatment can be stopped at 6 months, these treatments are currently administered until either disease progression for some IO, 2 years for others, or unacceptable toxicity. However, a growing number of studies are reporting maintenance of response despite discontinuation of therapy. There is currently no evidence of a dose effect of IO in pharmacokinetic studies. Maintaining efficacy despite a reduction in treatment intensity by decreasing the frequency of administration in patients with highly selected metastatic cancer, is the hypothesis evaluated in the MOIO study.

METHOD/DESIGN

This non-inferiority, randomized phase III study aims to compare the standard regimen to a 3 monthly regimen of variousIO drugs in adult patients with metastatic cancer in partial (PR) or complete response (CR) after 6 months of standard IO dosing (except melanoma in CR). This is a French national study conducted in 36 centers. The main objective is to demonstrate that the efficacy of a three-monthly administration is not unacceptably less efficacious than a standard administration. Secondary objectives are cost-effectiveness, quality of life (QOL), anxiety, fear of relapse, response rate, overall survival and toxicity. After 6 months of standard IO, patients with partial or complete response will be randomized 1:1 between standard IO or a reduced intensity dose of IO, administered every 3 months. The randomization will be stratified on therapy line,, tumor type, IO type and response status. The primary endpoint is the hazard ratio of progression-free survival. With a planned study duration of 6 years, including 36 months enrolment time, 646 patients are planned to demonstrate with a statistical level of evidence of 5% that the reduced IO regimen is non-inferior to the standard IO regimen, with a relative non-inferiority margin set at 1.3.

DISCUSSION

Should the hypothesis of non-inferiority with an IO reduced dose intensity be validated, alternate scheduling could preserve efficacy while being cost-effective and allowing a reduction of the toxicity, with an increase in patient's QOL.

TRIAL REGISTRATION

NCT05078047.

Dosing Regimens of Immune Checkpoint Inhibitors: Attempts at Lower Dose, Less Frequency, Shorter Course

Immune checkpoint inhibitors (ICIs) are a revolutionary breakthrough in the field of cancer by modulating patient's own immune system to exert anti-tumor effects. The clinical application of ICIs is still in its infancy, and their dosing regimens need to be continuously adjusted. Pharmacokinetic/pharmacodynamic studies showed a significant plateau in the exposure-response curve, with high receptor occupancy and plasma concentrations achieved at low dose levels. Coupled with concerns about drug toxicity and heavy economic costs, there has been an ongoing quest to reevaluate the current ICI dosing regimens while preserving maximum clinical efficacy. Many clinical data showed remarkable anticancer effects with ICIs at the doses far below the approved regimens, indicating the possibility of dose reduction. Our review attempts to summarize the clinical evidence for ICIs regimens with lower-dose, less-frequency, shorter-course, and provide clues for further ICIs regimen optimization.

Review of the Clinical Pharmacokinetics, Efficacy and Safety of Pembrolizumab

BACKGROUND

Treatment of various types of cancer has been improved significantly with the discovery of biologic drugs that act as immune checkpoint inhibitors (ICIs). Pembrolizumab is a humanized monoclonal anti-PD-1 antibody currently approved for the treatment of a wide range of tumors, with more indications still being investigated in ongoing clinical trials.

OBJECTIVE

The aim of this paper is to present all currently available data regarding pembrolizumab pharmacokinetic and pharmacodynamic characteristics. Also, the possibility of using predicative biomarkers to monitor patients during cancer treatment is discussed.

METHODS

Database research was carried out (PubMed, ScienceDirect). Information was gathered from original articles, the European Medicines Agency datasheets and results from clinical trials.

RESULTS

This review summarizes present-day knowledge about the pharmacokinetics, different modeling approaches and dosage regimens, efficacy and safety of pembrolizumab and therapeutic monitoring of disease progression.

CONCLUSION

This review points out consistent pharmacokinetic characteristics of pembrolizumab in various cancer patients, the lack of pharmacokinetic-pharmacodynamic/outcome relationships, the need of adequate biomarkers predicting treatment success. Hence, there is a clear necessity for more data and experience in order to optimize pembrolizumab treatment for each individual patient.

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.

Pharmacokinetic Simulation Analysis of Less Frequent Nivolumab and Pembrolizumab Dosing: Pharmacoeconomic Rationale for Dose Deescalation

Nivolumab and pembrolizumab, anti-programmed cell death protein 1 monoclonal antibodies, have revolutionized oncology but are expensive. Using an interventional pharmacoeconomic approach, these drugs can be administered less often to reduce costs and increase patient convenience while maintaining efficacy. Both drugs are good candidates for less frequent dosing because of long half-lives and no evidence of a relationship of dose to efficacy. Established population pharmacokinetic models for both nivolumab and pembrolizumab were used to simulate profiles for multiple dosing regimens on 1000 randomly generated virtual patients. Simulations were initially performed on standard dose regimens to validate these in silico predictions. Next, simulations of nivolumab 0.3 mg/kg every 3 weeks revealed that >95% of patients maintained ≥1.5 μg/mL at steady state, which was inferred as the minimum effective concentration (MEC) for both drugs. Various alternative dosing regimens were simulated for both drugs to determine which regimen(s) can maintain this MEC in >95% of patients. Extended dosing regimens of nivolumab 240 mg every 4 weeks and 480 mg every 8 weeks along with pembrolizumab 200 mg every 6 weeks were simulated, showing that >95% of patients maintained MEC or greater. These simulations demonstrate the potential to reduce drug exposure by at least 50%, thus substantially reducing patient visits (as well as costs), while maintaining equivalent efficacy. These models provide the scientific justification for an ongoing prospective randomized clinical trial comparing standard interval fixed dosing with extended interval fixed dosing, and ultimately an efficacy-driven comparative trial.

Immune checkpoint-targeted antibodies: a room for dose and schedule optimization?

Anti-CTLA-4 and anti-PD-1/PD-L1 immune checkpoint inhibitors are therapeutic monoclonal antibodies that do not target cancer cells but are designed to reactivate or promote antitumor immunity. Dosing and scheduling of these biologics were established according to conventional drug development models, even though the determination of a maximum tolerated dose in the clinic could only be defined for anti-CTLA-4. Given the pharmacology of these monoclonal antibodies, their high interpatient pharmacokinetic variability, the actual clinical benefit as monotherapy that is observed only in a specific subset of patients, and the substantial cost of these treatments, a number of questions arise regarding the selected dose and the dosing interval. This review aims to outline the development of these immunotherapies and considers optimization options that could be used in clinical practice.

Cross-Validation of a Multiplex LC-MS/MS Method for Assaying mAbs Plasma Levels in Patients with Cancer: A GPCO-UNICANCER Study

BACKGROUND

Different liquid chromatography tandem mass spectrometry (LC-MS/MS) methods have been published for quantification of monoclonal antibodies (mAbs) in plasma but thus far none allowed the simultaneous quantification of several mAbs, including immune checkpoint inhibitors. We developed and validated an original multiplex LC-MS/MS method using a ready-to-use kit to simultaneously assay 7 mAbs (i.e., bevacizumab, cetuximab, ipilimumab, nivolumab, pembrolizumab, rituximab and trastuzumab) in plasma. This method was next cross-validated with respective reference methods (ELISA or LC-MS/MS).

METHODS

The mAbXmise kit was used for mAb extraction and full-length stable-isotope-labeled antibodies as internal standards. The LC-MS/MS method was fully validated following current EMA guidelines. Each cross validation between reference methods and ours included 16-28 plasma samples from cancer patients.

RESULTS

The method was linear from 2 to 100 µg/mL for all mAbs. Inter- and intra-assay precision was <14.6% and accuracy was 90.1-111.1%. The mean absolute bias of measured concentrations between multiplex and reference methods was 10.6% (range 3.0-19.9%).

CONCLUSIONS

We developed and cross-validated a simple, accurate and precise method that allows the assay of up to 7 mAbs. Furthermore, the present method is the first to offer a simultaneous quantification of three immune checkpoint inhibitors likely to be associated in patients.

Evaluating the efficacy and safety of immune checkpoint inhibitors by detecting the exposure-response: An inductive review

Immune checkpoint inhibitors (ICIs) have been demonstrated an effective treatment in multiple tumor type, which restore the immune response to against cancer cell. Currently, approved ICIs include anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4); anti-programmed cell death 1 (PD-1) and anti-programmed cell death ligand 1 (PD-L1) monoclonal antibodies (mAbs). In most these drugs, unique pharmacokinetic (PK) and pharmacodynamics (PD) have shown significant influence on clinical outcomes, which occurred by target-mediated drug concentration and time-varying drug clearance. An exposure-response (E-R) relationship has been used to describe the safety and efficacy of ICIs, and shown a plateaued E-R and time dependent changes in exposure. Using an enzyme linked immunosorbent assay (ELISA) or LC-MS/MS method to measure the peak concentration, trough concentration or area under the curve (AUC) of ICIs to assess the drug exposure. There are lots of covariates that have an influence on exposure, such as sex, clearance, body weight and tumor burden. In this review, we pooled data from studies of concentration or other pharmacokinetics parameter of mAbs to assess E-R in efficacy and safety.

The Right Dose: From Phase I to Clinical Practice

To realize the full potential of promising new anticancer drugs, it is of paramount importance to administer them at the right dose. The aim of this educational article is to provide several opportunities to optimize anticancer drug dosing, focusing on oral targeted therapies. First, therapeutic drug monitoring can optimize exposure in individual patients, if the optimal concentration is known. This approach is of particular interest in regard to oral kinase inhibitors with high interindividual pharmacokinetic variability. If exposure is related to response, then therapeutic drug monitoring is potentially feasible, although the clinical utility of this approach has not yet been established. Other approaches to reduce variability include administration of more frequent, smaller doses and administration under optimal prandial conditions. However, for many drugs, the labeled dose has not been demonstrated to be the optimal dose; for such agents, the vast majority of patients may be receiving excessive doses, which results in excessive toxicity. Furthermore, administration of lower off-label doses may reduce both medical and financial toxicity. These strategies should be applied from registration studies to clinical practice, with the goal of better optimizing anticancer treatment.

Dosage of anti-PD-1 monoclonal antibodies: a cardinal open question

Discovery and clinical development of monoclonal antibodies with the ability to interfere in the regulation of the immune response have significantly changed the landscape of oncology in recent years. Among the active agents licensed by the regulatory agencies, nivolumab and pembrolizumab are paradigmatic as the most relevant ones according to the magnitude of available data derived from the extensive preclinical and clinical experience. Although in both cases the respective data sheets indicate well-defined dosage regimens, a review of the literature permits to verify the existence of many issues still unresolved about dosing the two agents, so it must be considered an open question of potentially important consequences, in which to work to improve the effectiveness and efficiency of use.

Direct analysis in real time-mass spectrometry for rapid quantification of five anti-arrhythmic drugs in human serum: application to therapeutic drug monitoring

Therapeutic drug monitoring (TDM) is necessary for the optimal administration of anti-arrhythmic drugs in the treatment of heart arrhythmia. The present study aimed to develop and validate a direct analysis in real time tandem mass spectrometry (DART–MS/MS) method for the rapid and simultaneous determination of five anti-arrhythmic drugs (metoprolol, diltiazem, amiodarone, propafenone, and verapamil) and one metabolite (5-hydroxy(OH)-propafenone) in human serum. After the addition of isotope-labeled internal standards and protein precipitation with acetonitrile, anti-arrhythmic drugs were ionized by DART in positive mode followed by multiple reaction monitoring (MRM) detection. The use of DART–MS/MS avoided the need for chromatographic separation and allowed rapid and ultrahigh throughput analysis of anti-arrhythmic drugs in a total run time of 30 s per sample. The DART–MS/MS method yielded satisfactory linearity (R² ≥ 0.9906), accuracy (86.1–109.9%), and precision (≤ 14.3%) with minimal effect of biological matrixes. The method was successfully applied to analyzing 30 clinical TDM samples. The relative error (RE) of the concentrations obtained by DART–MS/MS and liquid chromatography-tandem mass spectrometry (LC–MS/MS) was within ± 13%. This work highlights the potential usefulness of DART for the rapid quantitative analysis of anti-arrhythmic drugs in human serum and gives rapid feedback in the clinical TDM practices.

Opportunities for using in silico-based extended dosing regimens for monoclonal antibody immune checkpoint inhibitors

Therapeutic drug monitoring (TDM) involves frequent measurements of drug concentrations to ensure levels remain within a therapeutic window, and it is especially useful for drugs with narrow therapeutic indices or extensive interindividual pharmacokinetic variability. This technique has never been applied to immuno-oncology drugs, but, given recent examinations of clinical data (both exposure and response) on a number of these drugs, further investigations into TDM may be justified to reduce costs as well as potentially reducing the severity and/or duration of immune-related adverse events. Specifically, all but one of the approved PD-1 and PD-L1 inhibitors (pembrolizumab, nivolumab, cemiplimab-rwlc, atezolizumab, avelumab, durvalumab) have been shown to exhibit a plateaued exposure-response (E-R) curve at doses evaluated extensively to date, as well as time-dependent changes in drug exposure. Furthermore, responders have a greater decrease in drug clearance over time and would, therefore, have supratherapeutic serum concentrations. With frequent trough measurements, it is possible to use pharmacokinetic modelling and simulation to estimate drug clearance via Bayesian methods. Based on patient-specific estimates for clearance, optimal alternative dosing strategies can be simulated to lower drug and cost burden yet maintain therapeutic levels, especially as the clearance of the drug decreases over time. This review will comprehensively discuss each of the FDA approved PD-1, PD-L1/2 and CTLA-4 inhibitors regarding their indications and current recommended dosing, with evidence supporting the investigation of these types of TDM strategies.

Model-based simulation to support the extended dosing regimens of atezolizumab

PURPOSE

The currently recommended dosages of atezolizumab for patients with non-small cell lung cancer (NSCLC) and urothelial carcinoma (UC) is 840 mg every 2 weeks, 1200 mg every 3 weeks (q3w), and 1680 mg every 4 weeks (q4w). However, it has been argued that these dosages may not be optimal. This study aimed to explore the feasibility of extended dosing regimens by population pharmacokinetics (PK) simulations and exposure-response (E-R) relationships.

METHODS

All simulations were conducted based on the established population PK and E-R model for safety (i.e., adverse events of special interest, AESI) and efficacy (i.e., objective response rate, ORR) for patients with NSCLC or UC. The PK, AESI, and ORR profiles of the following dosing regimens were simulated: (i) 840 mg q4w, (ii) 1200 mg every 6 weeks (q6w), and (iii) 1680 mg q8w. These regimens were compared with those of the 1200 mg q3w standard regimen.

RESULTS

The simulation revealed that the ranking of efficacy for different extended dosing regimens were 1680 mg q8w ≅ 1200 mg q3w ≅ 1200 mg q6w > 840 mg q4w based on the predicted probability of ORR in patients with NSCLC and UC, and this ranking order was similar to that of the safety outcome of the AESI. The minimum serum concentration at steady-state (C_min,ss) values for all dosing regimens was all higher than the target effective concentration of 6 μg/mL.

CONCLUSION

The findings from this simulation suggest that extended dosing regimens are unlikely to significantly impair clinical outcomes and may provide more therapeutic benefits to patients in terms of safety.