PBPK model for antibody disposition in mouse brain: validation using large-pore microdialysis data.

The objective of this manuscript was to validate a physiologically-based pharmacokinetic (PBPK) model developed to characterize brain pharmacokinetics (PK) of monoclonal antibodies (mAbs) using novel large-pore microdialysis data generated in mice. To support this objective, brain, CSF, and ISF PK of a human anti-tetanus toxin (TeTx) antibody was measured in mice following intraperitoneal (IP) administration. This antibody has no binding in mice. In addition, our recently published mouse brain PK data generated following intravenous (IV) and IP administration of trastuzumab in mice, and other published PK data for brain disposition of antibody in mice, were used to evaluate the PBPK model. All the model parameters were obtained from literature or kept the same as in our previously published manuscript. The revised PBPK model was able to characterize the PK of antibodies in mice brain, CSF, and ISF reasonably well (i.e., within a three-fold error). However, a priori selected parameters led to underprediction of ISF PK during the initial phase of the profile. A local sensitivity analysis suggested that minor changes in several brain-related parameters can help overcome this discrepancy, where an increase in the convective flow of antibodies across BBB was found to be the most parsimonious way to capture all the PK profiles well. However, the presence of this pathway needs further validation. As such, here we have presented an improved PBPK model to characterize and predict the PK of mAbs in different regions of the mouse brain following systemic administration. This model can serve as a quantitative tool to facilitate the discovery, preclinical evaluation, and preclinical-to-clinical translation of novel antibodies targeted against CNS disorders.

High-dose methotrexate is effective for prevention of isolated CNS relapse in diffuse large B cell lymphoma.

The role of central nervous system (CNS) prophylaxis with high-dose methotrexate (HDMTX) in DLBCL is controversial. In this retrospective study, we evaluated the efficacy of prophylactic HDMTX on isolated CNS relapse, concomitant CNS and systemic relapse, systemic relapse, and survival outcomes in 226 patients with newly diagnosed DLBCL and high-risk CNS International Prognostic Index (CNS-IPI) score treated with RCHOP. The three-year risk of isolated CNS relapse was significantly lower in patients who received HDMTX, at 3.1% compared to 14.6% (P = 0.032) in those who did not. However, neither concomitant CNS-systemic relapse rates, systemic relapse rates, nor three-year PFS and OS were significantly different between treatment groups in multivariable analysis. Among propensity score-matched patients (N = 102), HDMTX was also associated with significantly lower isolated CNS relapse rates (HR 0.06, 95% CI 0.004-0.946, P = 0.046). HDMTX was well tolerated with manageable toxicities when given at a dose of 3 g/m2 by day 3 of RCHOP chemotherapy. Using propensity score matching and multivariable regression to yield treatment groups with well-balanced covariates, we showed that prophylactic HDMTX improved isolated CNS relapse rates but did not decrease concomitant CNS-systemic relapse rates, systemic relapse rates, or improve survival outcomes.

HEMATOPOIETIC STEM CELL TRANSPLANT IN AGGRESSIVE T AND NK/T CELL LYMPHOMA - ROLE OF UPFRONT AUTOLOGOUS TRANSPLANT IN NODAL PERIPHERAL T-CELL LYMPHOMA.

Aggressive T and NK/T-cell lymphoma are known to have a high risk of relapse and poor long-term prognosis. Hematopoietic stem cell transplantation has been performed as part of consolidation or salvage treatment. We retrospectively studied the outcomes of autologous (A) and allogeneic (allo) hematopoietic stem cell transplantation (SCT) in aggressive T and NK/T-cell lymphoma at our center between 2010 to 2020. Patients with nodal peripheral T-cell lymphoma (PTCL) that were younger than 65 years old who did not receive upfront autologous SCT (ASCT) at first complete remission were selected from our registry data for further comparison. Thirty-six patients underwent ASCT, and 16 patients underwent alloSCT. In the ASCT cohort, 18 patients with nodal PTCL who underwent upfront ASCT at first complete remission (upfront ASCT) were compared with 15 patients with nodal PTCL who were in first complete remission after single-line induction but did not receive ASCT. The two-year progression-free survival (PFS) and overall survival (OS) rates for the ASCT cohort were 58% and 73%, respectively. The two-year PFS and OS for the alloSCT cohort were 47% (P=0.35, P=0.02, respectively). Twenty-four patients who received SCT at first remission (21 ASCT and three alloSCT) had a two-year PFS and OS of 75% and 89%, respectively. In comparison, 28 patients who received SCT at relapse/refractory (15 ASCT and 13 alloSCT) had a two-year PFS and OS of 40% and 50%, respectively (P=0.047, P=0.024, respectively). Patients in complete remission prior to transplantation (n=42) had a two-year PFS and OS of 59% and 73%, respectively. In contrast, patients in partial remission prior to transplantation (n=10) had a two-year PFS and OS of 40% and 48%, respectively (p>0.05). Non-relapse mortality occurred in 6% and 43% of ASCT and AlloSCT, respectively. Multivariate analysis revealed that EBV-positivity at diagnosis indicated poorer PFS. EBV-positivity at diagnosis and more than two prior lines of treatment at transplant were associated with poorer OS. For nodal PTCL, the two-year PFS and OS were 79% and 100% for the upfront ASCT cohort and 78% and 92% for the non-upfront ASCT cohort, respectively (p>0.05). Hematopoietic SCT is a feasible treatment option for aggressive T and NK/T-cell lymphoma. Patients who underwent SCT at first remission had better survival rates than those who underwent SCT at relapse/refractory. Nevertheless, due to the limited sample size of the current study, the role of upfront ASCT in patients with nodal PTCL who achieved first complete remission remains unclear.

Antibody-drug conjugates as targeted therapies: Are we there yet? A critical review of the current clinical landscape.

Antibody-drug conjugates (ADCs) are targeted therapies with the expectation of broadened therapeutic window due to tumor-specific drug delivery. Recent approvals, including ADCs with a novel payload class, topoisomerase-1 inhibitors, generated renewed excitement in the field. We provide a critical review of approved and late-stage molecules, discuss strategies in solid tumors and ADCs outside oncology. Our pharmacokinetics-based assessment of targeting suggests that ADCs, especially in solid tumors, rely on additional mechanisms for efficacy including slow-release of the payload to the circulation at potentially efficacious levels. Further adjustments in the technology are needed to fulfill the promise of true targeted drug delivery.

Mechanistic Modeling of Antibody-Drug Conjugate Internalization at the Cellular Level Reveals Inefficient Processing Steps.

Antibody-drug conjugates (ADC) offer an avenue for specific drug delivery to target cells. Here, parameters with important roles in the cellular processing of ADCs were quantitatively measured for Ab033, an antibody against EGFR. In EGFR-overexpressing cancer cell lines, Ab033 internalized at rates of 0.047/min and 0.15/min for A431 and H441 cells, respectively. Once internalized, Ab033 either trafficked to the lysosome or was recycled; up to 45% of internalized Ab033 returned to the cell surface. Despite such recycling, intracellular accumulation of Ab033 continually increased over 24 hours. Ab033 was conjugated to form a dual toxin ADC containing both cleavable and non-cleavable linker-drug payloads for release rate comparisons. Intracellular concentrations of freed drug from cleavable linker were greater than from non-cleavable linker and exceeded 5 × 106 drug molecules per A431 cell after 24 hours. Compared with intracellular antibody accumulation, formation of released drug was delayed, likely due to the time needed for endo-lysosomal trafficking and subsequent linker/antibody proteolysis. Informed by the quantitative data, a cellular ADC model was constructed and used to summarize processing inefficiencies. Modeling simulations were conducted to determine parameter sensitivity on intracellular drug concentrations, with rates of EGFR internalization and recycling as well as ADC trafficking found to be the most sensitive toward final intracellular drug concentrations. Overall, this study shows Ab033 ADCs to be a viable strategy for delivery of cytotoxic drugs into tumor cells with subsequent modeling efforts able to highlight key processing steps to be improved for increased drug delivery. Mol Cancer Ther; 17(6); 1341-51. ©2018 AACR.

The impact of time from diagnosis to treatment in diffuse large B-cell lymphoma.

Diffuse large B-cell lymphoma (DLBCL) is a high-grade lymphoma that requires treatment. We retrospectively analyzed the impact of time from diagnosis-to-treatment (TDT) on progression-free survival (PFS) and overall survival (OS) in 581 R-CHOP-treated patients. TDT was defined as the interval between diagnostic biopsy date and day 1 R-CHOP. Cox regression showed stage 3-4 disease (p = .01) and longer TDT (HR 1.13, p =.031) were associated with shorter OS. Eastern Cooperative Oncology Group ≥2 (p = .02), stage 3-4 disease (p < .001), and longer TDT (HR 1.12, p = .028) predicted shorter PFS. The significant interactions between TDT with lactate dehydrogenase (LDH) and with disease stage prompted separate analyses in high versus normal LDH, and stage 3-4 versus 1-2 disease. Longer TDT was associated with shortened PFS and OS only with advanced stage, and, if high LDH was present. Treatment should be started as early as possible for high-tumor burden disease. Delaying treatment in patients with early stage or low LDH does not seem harmful.

Quantifying the effects of antiangiogenic and chemotherapy drug combinations on drug delivery and treatment efficacy.

Tumor-induced angiogenesis leads to the development of leaky tumor vessels devoid of structural and morphological integrity. Due to angiogenesis, elevated interstitial fluid pressure (IFP) and low blood perfusion emerge as common properties of the tumor microenvironment that act as barriers for drug delivery. In order to overcome these barriers, normalization of vasculature is considered to be a viable option. However, insight is needed into the phenomenon of normalization and in which conditions it can realize its promise. In order to explore the effect of microenvironmental conditions and drug scheduling on normalization benefit, we build a mathematical model that incorporates tumor growth, angiogenesis and IFP. We administer various theoretical combinations of antiangiogenic agents and cytotoxic nanoparticles through heterogeneous vasculature that displays a similar morphology to tumor vasculature. We observe differences in drug extravasation that depend on the scheduling of combined therapy; for concurrent therapy, total drug extravasation is increased but in adjuvant therapy, drugs can penetrate into deeper regions of tumor.

Pharmacokinetic Considerations for Antibody-Drug Conjugates against Cancer.

Antibody-drug conjugates (ADCs) are ushering in the next era of targeted therapy against cancer. An ADC for cancer therapy consists of a potent cytotoxic payload that is attached to a tumour-targeted antibody by a chemical linker, usually with an average drug-to-antibody ratio (DAR) of 3.5-4. The theory is to deliver potent cytotoxic payloads directly to tumour cells while sparing healthy cells. However, practical application has proven to be more difficult. At present there are only two ADCs approved for clinical use. Nevertheless, in the last decade there has been an explosion of options for ADC engineering to optimize target selection, Fc receptor interactions, linker, payload and more. Evaluation of these strategies requires an understanding of the mechanistic underpinnings of ADC pharmacokinetics. Development of ADCs for use in cancer further requires an understanding of tumour properties and kinetics within the tumour environment, and how the presence of cancer as a disease will impact distribution and elimination. Key pharmacokinetic considerations for the successful design and clinical application of ADCs in oncology are explored in this review, with a focus on the mechanistic determinants of distribution and elimination.

Clinicopathological features and outcome of chronic lymphocytic leukaemia in Chinese patients.

Chronic lymphocytic leukaemia (CLL) is uncommon in Chinese population and its biology, genetics and treatment outcome in Chinese patients have not been comprehensively investigated. In this study, we studied the clinicopathological features and outcome of 212 Chinese patients with newly diagnosed CLL in Hong Kong and Singapore. The median age at diagnosis was 64 years. The majority of patients presented with early-stage disease (Binet stage A, 56.1%). Del(13)(q14) was the most frequent abnormality (41.7%) detected by fluorescence in situ hybridization (FISH) analysis. Del(17p) and TP53 gene mutations were detected in 7.8% and 8.2% of patients, respectively. MYD88 mutations were found at a higher frequency (11.5%) than expected. CLL with unmutated variable region of the immunoglobulin heavy chain genes (IGHV) occurred in only 31.2% of cases, and was associated with advanced-stage disease (p <0.01) and adverse FISH abnormalities (p<0.01). With a median follow-up of 39 months, the median overall survival (OS) was 108 months. The presence of del(17p) or TP53 mutations was associated with a significantly shorter time to first treatment and an inferior OS (p <0.01). Unmutated IGHV was also associated with a significantly shorter time to treatment (p <0.01). Among patients who required treatment, the median OS and progression-free survival (PFS) were 107 and 23 months, respectively. The presence of del(17p) was associated with a significantly inferior OS and PFS (p <0.01). In summary, Chinese CLL patients had similar genetic aberrations at diagnosis compared with those of Western populations. FISH abnormalities are major factors affecting outcome.

Population PBPK modelling of trastuzumab: a framework for quantifying and predicting inter-individual variability.

In this work we proposed a population physiologically-based pharmacokinetic (popPBPK) framework for quantifying and predicting inter-individual pharmacokinetic variability using the anti-HER2 monoclonal antibody (mAb) trastuzumab as an example. First, a PBPK model was developed to account for the possible mechanistic sources of variability. Within the model, five key factors that contribute to variability were identified and the nature of their contribution was quantified with local and global sensitivity analyses. The five key factors were the concentration of membrane-bound HER2 ([Formula: see text]), the convective flow rate of mAb through vascular pores ([Formula: see text]), the endocytic transport rate of mAb through vascular endothelium ([Formula: see text]), the degradation rate of mAb-HER2 complexes ([Formula: see text]) and the concentration of shed HER2 extracellular domain in circulation ([Formula: see text]). [Formula: see text] was the most important parameter governing trastuzumab distribution into tissues and primarily affected variability in the first 500 h post-administration. [Formula: see text] was the most significant contributor to variability in clearance. These findings were used together with population generation methods to accurately predict the observed variability in four experimental trials with trastuzumab. To explore anthropometric sources of variability, virtual populations were created to represent participants in the four experimental trials. Using populations with only their expected anthropometric diversity resulted in under-prediction of the observed inter-individual variability. Adapting the populations to include literature-based variability around the five key parameters enabled accurate predictions of the variability in the four trials. The successful application of this framework demonstrates the utility of popPBPK methods to understand the mechanistic underpinnings of pharmacokinetic variability.

PD1 blockade with pembrolizumab is highly effective in relapsed or refractory NK/T-cell lymphoma failing l-asparaginase.

Natural killer (NK)/T-cell lymphomas failing L-asparaginse regimens have no known salvage and are almost invariably fatal. Seven male patients with NK/T-cell lymphoma (median age, 49 years; range, 31-68 years) for whom a median of 2 (range, 1-5) regimens (including l-asparaginase regimens and allogeneic hematopoietic stem-cell transplantation [HSCT] in 2 cases) failed were treated with the anti-programmed death 1 (PD1) antibody pembrolizumab. All patients responded, according to various clinical, radiologic (positron emission tomography), morphologic, and molecular (circulating Epstein-Barr virus [EBV] DNA) criteria. Two patients achieved complete response (CR) in all parameters. Three patients achieved clinical and radiologic CRs, with two having molecular remission (undetectable EBV DNA) but minimal EBV-encoded RNA-positive cells in lesions comprising predominantly CD3+CD4+ and CD3+CD8+ T cells (which ultimately disappeared, suggesting they represented pseudoprogression) and one having detectable EBV DNA despite morphologic CR. Two patients achieved partial response (PR). After a median of 7 (range, 2-13) cycles of pembrolizumab and a follow-up of a median of 6 (range, 2-10) months, all five CR patients were still in remission. The only adverse event was grade 2 skin graft-versus-host disease in one patient with previous allogeneic HSCT. Expression of the PD1 ligand was strong in 4 patients (3 achieving CR) and weak in 1 (achieving PR). PD1 blockade with pembrolizumab was a potent strategy for NK/T-cell lymphomas failing l-asparaginase regimens.

Drug-induced reactive oxygen species (ROS) rely on cell membrane properties to exert anticancer effects.

Pharmacological concentrations of small molecule natural products, such as ascorbic acid, have exhibited distinct cell killing outcomes between cancer and normal cells whereby cancer cells undergo apoptosis or necrosis while normal cells are not adversely affected. Here, we develop a mathematical model for ascorbic acid that can be utilized as a tool to understand the dynamics of reactive oxygen species (ROS) induced cell death. We determine that not only do endogenous antioxidants such as catalase contribute to ROS-induced cell death, but also cell membrane properties play a critical role in the efficacy of ROS as a cytotoxic mechanism against cancer cells vs. normal cells. Using in vitro assays with breast cancer cells, we have confirmed that cell membrane properties are essential for ROS, in the form of hydrogen peroxide (H2O2), to induce cell death. Interestingly, we did not observe any correlation between intracellular H2O2 and cell survival, suggesting that cell death by H2O2 is triggered by interaction with the cell membrane and not necessarily due to intracellular levels of H2O2. These findings provide a putative mechanistic explanation for the efficacy and selectivity of therapies such as ascorbic acid that rely on ROS-induced cell death for their anti-tumor properties.