Challenges and Lessons Learned in Autologous Chimeric Antigen Receptor T-Cell Therapy Development from a Statistical Perspective.

Chimeric antigen receptor (CAR) T-cell therapy is a human gene therapy product where T cells from a patient are genetically modified to enable them to recognize desired target antigen(s) more effectively. In recent years, promising antitumor activity has been seen with autologous CAR T cells. Since 2017, six CAR T-cell therapies for the treatment of hematological malignancies have been approved by the Food and Drug Administration (FDA). Despite the rapid progress of CAR T-cell therapies, considerable statistical challenges still exist for this category of products across all phases of clinical development that need to be addressed. These include (but not limited to) dose finding strategy, implementation of the estimand framework, use of real-world data in contextualizing single-arm CAR T trials, analysis of safety data and long-term follow-up studies. This paper is the first step in summarizing and addressing these statistical hurdles based on the development of the six approved CAR T-cell products.

Phase 2 results of idecabtagene vicleucel (ide-cel, bb2121) in Japanese patients with relapsed and refractory multiple myeloma.

BACKGROUND: In the phase 2 KarMMa trial, patients with relapsed/refractory multiple myeloma (RRMM) achieved deep and durable responses with idecabtagene vicleucel (ide-cel), a B-cell maturation antigen-directed chimeric antigen receptor (CAR) T cell therapy. Here we report a sub-analysis of the Japanese cohort of KarMMa. METHODS: Adult patients with RRMM who had received  ≥ 3 prior treatment regimens, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 antibody, and had disease refractory to last treatment received ide-cel at a target dose of 450 × 106 CAR positive T cells. RESULTS: Nine patients were treated with ide-cel. The overall response rate was 89% (median follow-up, 12.9 months). The best overall response was stringent complete response in 5 patients (56%), very good partial response in 3 (33%), and stable disease in 1. Median duration of response was not reached. All patients experienced grade ≤ 2 cytokine release syndrome and one patient experienced grade 2 neurotoxicity, but all resolved. Two patients died, one each from plasma cell myeloma and general health deterioration. CONCLUSION: Ide-cel yielded deep, durable responses with a tolerable and predictable safety profile in Japanese patients with RRMM. These results are similar to those of the non-Japanese population in KarMMa.

An overview of the BOIN design and its current extensions for novel early-phase oncology trials.

Bayesian Optimal Interval (BOIN) designs are a class of model-assisted dose-finding designs that can be used in oncology trials to determine the maximum tolerated dose (MTD) of a study drug based on safety or the optimal biological dose (OBD) based on safety and efficacy. BOIN designs provide a complete suite for dose finding in early phase trials, as well as a consistent way to explore different scenarios such as toxicity, efficacy, continuous outcomes, delayed toxicity or efficacy and drug combinations in a unified manner with easy access to software to implement most of these designs. Although built upon Bayesian probability models, BOIN designs are operationally simple in general and have good statistical operating characteristics compared to other dose-finding designs. This review paper describes the original BOIN design and its many extensions, their advantages and limitations, the software used to implement them, and the most suitable situation for use of each of these designs. Published examples of the implementation of BOIN designs are provided in the Appendix.

Phase 2 results of lisocabtagene maraleucel in Japanese patients with relapsed/refractory aggressive B-cell non-Hodgkin lymphoma.

The autologous anti-CD19 chimeric antigen receptor (CAR) T-cell product, lisocabtagene maraleucel (liso-cel), is administered at equal target doses of CD8+ and CD4+ CAR+ T cells. This analysis assessed safety and efficacy of liso-cel in Japanese patients with relapsed or refractory (R/R) aggressive large B-cell lymphoma (LBCL) in Cohort 3 of TRANSCEND WORLD (NCT03484702). Liso-cel (100 × 106 total CAR+ T cells) was administered 2-7 days after lymphodepletion. The primary efficacy endpoint was objective response rate (ORR; Lugano 2014 criteria) assessed by an independent review committee. Fourteen patients were enrolled; 10 received liso-cel infusion (median time to liso-cel availability, 23 days) and were evaluable at data cutoff (median follow-up, 12.5 months). Grade ≥ 3 treatment-emergent adverse events were neutropenia (90%), leukopenia (80%), anemia (70%), and thrombocytopenia (70%). All-grade cytokine release syndrome (CRS) was observed in 50% of patients, though no grade ≥3 CRS events were reported. Grade 1 neurological events occurred in 1 patient but were resolved without any intervention. Prolonged cytopenia (grade ≥ 3 at day 29) was reported for 60% of patients. The ORR was 70%, and complete response rate was 50%. The median duration of response was 9.1 months (95% confidence interval [CI], 2.1-not reached), and overall survival was 14.7 months (95% CI, 1.7-not reached). One patient diagnosed with central nervous system involvement after screening but before liso-cel infusion, responded to liso-cel. Liso-cel demonstrated meaningful efficacy and a manageable safety profile in Japanese patients with R/R LBCL.

Critical review of oncology clinical trial design under non-proportional hazards.

In trials of novel immuno-oncology drugs, the proportional hazards (PH) assumption often does not hold for the primary time-to-event (TTE) efficacy endpoint, likely due to the unique mechanism of action of these drugs. In practice, when it is anticipated that PH may not hold for the TTE endpoint with respect to treatment, the sample size is often still calculated under the PH assumption, and the hazard ratio (HR) from the Cox model is still reported as the primary measure of the treatment effect. Sensitivity analyses of the TTE data using methods that are suitable under non-proportional hazards (non-PH) are commonly pre-planned. In cases where a substantial deviation from the PH assumption is likely, we suggest designing the trial, calculating the sample size and analyzing the data, using a suitable method that accounts for non-PH, after gaining alignment with regulatory authorities. In this comprehensive review article, we describe methods to design a randomized oncology trial, calculate the sample size, analyze the trial data and obtain summary measures of the treatment effect in the presence of non-PH. For each method, we provide examples of its use from the recent oncology trials literature. We also summarize in the Appendix some methods to conduct sensitivity analyses for overall survival (OS) when patients in a randomized trial switch or cross-over to the other treatment arm after disease progression on the initial treatment arm, and obtain an adjusted or weighted HR for OS in the presence of cross-over. This is an example of the treatment itself changing at a specific point in time - this cross-over may lead to a non-PH pattern of diminishing treatment effect.

2D (2 Dimensional) TEQR design for Determining the optimal Dose for safety and efficacy.

Designs, such as the Eff-Tox, OBD (optimal biological dose), STEIN (simple efficacy toxicity interval), and TEPI (toxicity efficacy probability interval) designs, have been proposed to determine the optimal dose of a new oncology drug using both efficacy and toxicity. The goal of these designs is to select the optimal drug dose for further phase trials more accurately than dose finding designs that only consider toxicity, such as the 3 + 3, TEQR (toxicity equivalence range), mTPI (modified toxicity probability interval), and EWOC (escalation with overdose control) designs. We propose a new frequentist design for optimal dose selection, the 2D TEQR design, that is easier to understand and simpler to implement than the TEPI, Eff-Tox, STEIN and OBD designs, as it is based on the empirical or observed toxicity and efficacy rates and does not require specialized computations. We compare the performance of this new design with those of the TEPI, STEIN, Eff-Tox and OBD Isotonic designs. Although for the same sample size and cohort size, the frequentist 2D TEQR design is less accurate than the Bayesian TEPI design and also the STEIN design in selecting the optimal dose, the accuracy of optimal dose selection of the 2D TEQR design can be increased, in many cases, with a moderate increase in cohort size. The 2D TEQR design is as accurate as or more accurate than the Eff-Tox design in optimal dose selection, and better than the OBD Isotonic design, unless there is a clear peak in the true response rates, in which case the OBD Isotonic design performs better than the other designs.

Extensions of the mTPI and TEQR designs to include non-monotone efficacy in addition to toxicity for optimal dose determination for early phase immunotherapy oncology trials.

With the emergence of immunotherapy and other novel therapies, the traditional assumption that the efficacy of the study drug increases monotonically with dose levels is not always true. Therefore, dose-finding methods evaluating only toxicity data may not be adequate. In this paper, we have first compared the Modified Toxicity Probability Interval (mTPI) and Toxicity Equivalence Range (TEQR) dose-finding oncology designs for safety with identical stopping rules; we have then extended both designs to include efficacy in addition to safety - we determine the optimal dose for safety and efficacy using these designs by applying isotonic regression to the observed toxicity and efficacy rates, once the early phase trial is completed. We consider multiple types of underlying dose response curves, i.e., monotonically increasing, plateau, or umbrella-shaped. We conduct simulation studies to investigate the operating characteristics of the two proposed designs and compare them to existing designs. We found that the extended mTPI design selects the optimal dose for safety and efficacy more accurately than the other designs for most of the scenarios considered.

Phase 1 study of inotuzumab ozogamicin combined with R-GDP for the treatment of patients with relapsed/refractory CD22+ B-cell non-Hodgkin lymphoma.

Objective: To evaluate safety, tolerability, and preliminary activity of inotuzumab ozogamicin (InO) plus rituximab, gemcitabine, dexamethasone, and cisplatin (R-GDP) in patients with relapsed/refractory CD22+ B-cell non-Hodgkin lymphoma (NHL). Methods: Patients received InO plus R-GDP (21-day cycle; six-cycle maximum) using up-and-down dose-escalation schema for gemcitabine and cisplatin to define the highest dosage regimen(s) with acceptable toxicity (Part 1; n = 27). Part 2 (n = 10) confirmed safety and tolerability; Part 3 (n = 18) evaluated preliminary efficacy. Results: Among 55 patients enrolled, 42% were refractory at baseline (median 2 [range, 1-6] prior therapies); 38% had diffuse large B-cell lymphoma (DLBCL). The highest dosage regimen with acceptable toxicity was InO 0.8 mg/m2, rituximab 375 mg/m2, cisplatin 50 mg/m2, gemcitabine 500 mg/m2 (day 1 only) and dexamethasone 40 mg (days 1-4); this was confirmed in Part 2, in which three patients had dose-limiting toxicities (grade 4 thrombocytopenia [n = 2], febrile neutropenia [n = 2]). Most frequent treatment-related adverse events were thrombocytopenia (any grade, 85%; grade ≥3, 75%) and neutropenia (69%; 62%). Overall (objective) response rate (ORR) was 53% (11 complete, 18 partial responses); ORR was 71%, 33%, and 62% in patients with follicular lymphoma (n = 14), DLBCL (n = 21), and mantle cell lymphoma (n = 13), respectively. Conclusions: InO 0.8 mg/m2 plus R-GDP was associated with manageable toxicity, although gemcitabine and cisplatin doses were lower than in the standard R-GDP regimen due to hematologic toxicity. Evidence of antitumor activity was observed; however, these exploratory data should be interpreted with caution due to the small sample size and short follow-up duration (Clinicaltrials.gov number: NCT01055496).

Systematic comparison of the statistical operating characteristics of various Phase I oncology designs.

Dose finding Phase I oncology designs can be broadly categorized as rule based, such as the 3 + 3 and the accelerated titration designs, or model based, such as the CRM and Eff-Tox designs. This paper systematically reviews and compares through simulations several statistical operating characteristics, including the accuracy of maximum tolerated dose (MTD) selection, the percentage of patients assigned to the MTD, over-dosing, under-dosing, and the trial dose-limiting toxicity (DLT) rate, of eleven rule-based and model-based Phase I oncology designs that target or pre-specify a DLT rate of ∼0.2, for three sets of true DLT probabilities. These DLT probabilities are generated at common dosages from specific linear, logistic, and log-logistic dose-toxicity curves. We find that all the designs examined select the MTD much more accurately when there is a clear separation between the true DLT rate at the MTD and the rates at the dose level immediately above and below it, such as for the DLT rates generated using the chosen logistic dose-toxicity curve; the separations in these true DLT rates depend, in turn, not only on the functional form of the dose-toxicity curve but also on the investigated dose levels and the parameter set-up. The model based mTPI, TEQR, BOIN, CRM and EWOC designs perform well and assign the greatest percentages of patients to the MTD, and also have a reasonably high probability of picking the true MTD across the three dose-toxicity curves examined. Among the rule-based designs studied, the 5 + 5 a design picks the MTD as accurately as the model based designs for the true DLT rates generated using the chosen log-logistic and linear dose-toxicity curves, but requires enrolling a higher number of patients than the other designs. We also find that it is critical to pick a design that is aligned with the true DLT rate of interest. Further, we note that Phase I trials are very small in general and hence may not provide accurate estimates of the MTD. Thus our work provides a map for planning Phase I oncology trials or developing new ones.

Inotuzumab ozogamicin in adults with relapsed or refractory CD22-positive acute lymphoblastic leukemia: a phase 1/2 study.

This study evaluated the safety, antitumor activity, pharmacokinetics, and pharmacodynamics of inotuzumab ozogamicin (InO) for CD22-positive relapsed/refractory acute lymphoblastic leukemia. In phase 1, patients received InO 1.2 (n = 3), 1.6 (n = 12), or 1.8 (n = 9) mg/m2 per cycle on days 1, 8, and 15 over a 28-day cycle (≤6 cycles). The recommended phase 2 dose (RP2D) was confirmed (expansion cohort; n = 13); safety and activity of InO were assessed in patients receiving the RP2D in phase 2 (n = 35) and in all treated patients (n = 72). The RP2D was 1.8 mg/m2 per cycle (0.8 mg/m2 on day 1; 0.5 mg/m2 on days 8 and 15), with reduction to 1.6 mg/m2 per cycle after complete remission (CR) or CR with incomplete marrow recovery (CRi). Treatment-related toxicities were primarily cytopenias. Four patients experienced treatment-related venoocclusive disease/sinusoidal obstruction syndrome (VOD/SOS; 1 fatal). Two VOD/SOS events occurred during treatment without intervening transplant; of 24 patients proceeding to poststudy transplant, 2 experienced VOD/SOS after transplant. Forty-nine (68%) patients had CR/CRi, with 41 (84%) achieving minimal residual disease (MRD) negativity. Median progression-free survival was 3.9 (95% confidence interval, 2.9-5.4) months; median overall survival was 7.4 (5.7-9.2) months for all treated patients, with median 23.7 (range, 6.8-29.8) months of follow-up for all treated patients alive at data cutoff. Achievement of MRD negativity was associated with higher InO exposure. InO was well tolerated and demonstrated high single-agent activity and MRD-negativity rates. This trial was registered at www.clinicaltrials.gov as #NCT01363297.

Phase I Study of Inotuzumab Ozogamicin Combined with R-CVP for Relapsed/Refractory CD22+ B-cell Non-Hodgkin Lymphoma.

PURPOSE: To evaluate the safety, preliminary efficacy, and pharmacokinetics of inotuzumab ozogamicin, an anti-CD22 antibody conjugated to calicheamicin, in combination with the immunochemotherapeutic regimen, rituximab, cyclophosphamide, vincristine, and prednisone (R-CVP), in patients with relapsed/refractory CD22+ B-cell non-Hodgkin lymphoma (NHL). EXPERIMENTAL DESIGN: In part 1 (n = 16), patients received inotuzumab ozogamicin plus R-CVP on a 21-day cycle with escalating doses of cyclophosphamide first then inotuzumab ozogamicin. Part 2 (n = 10) confirmed the safety and tolerability of the maximum tolerated dose (MTD), which required a dose-limiting toxicity rate of <33% in cycle 1 and <33% of patients discontinuing before cycle 3 due to treatment-related adverse events (AEs). Part 3 (n = 22) evaluated the preliminary efficacy of inotuzumab ozogamicin plus R-CVP. RESULTS: The MTD was determined to be standard-dose R-CVP plus inotuzumab ozogamicin 0.8 mg/m2 The most common treatment-related grade ≥3 AEs in the MTD cohort (n = 38) were hematologic: neutropenia (74%), thrombocytopenia (50%), lymphopenia (42%), and leukopenia (47%). Among the 48 patients treated in the study, 13 discontinued due to AEs, most commonly thrombocytopenia (n = 10). Overall, 13 patients died, including one death due to treatment-related pneumonia secondary to neutropenia. Among patients receiving the MTD (n = 38), the overall response rate (ORR) was 84% (n = 32), including 24% (n = 9) with complete response; the ORR was 100% for patients with indolent lymphoma (n = 27) and 57% for those with aggressive histology lymphoma (n = 21). CONCLUSIONS: Inotuzumab ozogamicin at 0.8 mg/m2 plus full dose R-CVP was associated with manageable toxicities and demonstrated a high rate of response in patients with relapsed/refractory CD22+ B-cell NHL. The study is registered at ClinicalTrials.gov (NCT01055496). Clin Cancer Res; 22(19); 4807-16. ©2016 AACR.

A phase 2 study of inotuzumab ozogamicin in patients with indolent B-cell non-Hodgkin lymphoma refractory to rituximab alone, rituximab and chemotherapy, or radioimmunotherapy.

This phase 2 study evaluated the efficacy and safety of inotuzumab ozogamicin (InO) in patients with indolent B-cell non-Hodgkin lymphoma (NHL) refractory to rituximab alone, rituximab plus chemotherapy or anti-CD20 radioimmunotherapy. Patients received InO 1·8 mg/m(2) intravenously on a 28-d cycle for a planned 4-8 cycles. The initial InO dose and schedule could be adjusted for tolerability and patients were allowed to receive 2 additional cycles (up to 8 total) after achieving a complete response (CR). The primary endpoint was overall response. Eighty-one patients were enrolled, among whom 48 (59%) received ≥3 InO cycles and 13 (16%) completed the treatment phase. The overall response rate was 67% (CR, 31%). Median (95% confidence interval) progression-free survival was 12·7 (8·9-26·9) months; median overall survival was not reached. Haematological adverse events (AEs) were common, particularly thrombocytopenia (74%) and neutropenia (56%). These were also the most common AEs leading to treatment discontinuation (37% and 11%, respectively); 58% of patients reported AEs leading to treatment discontinuation. InO demonstrated robust activity in these heavily pretreated patients, although treatment duration was limited by haematological toxicities. Additional studies may determine dosing regimens that allow for reduced toxicity.

Phase I study of neratinib in combination with temsirolimus in patients with human epidermal growth factor receptor 2-dependent and other solid tumors.

PURPOSE: Human epidermal growth factor (HER) -mediated signaling is critical in many cancers, including subsets of breast and lung cancer. HER family members signal via the phosphatidylinositide 3-kinase (PI3K) -AKT/protein kinase B-mammalian target of rapamycin (mTOR) cascade; mTOR activation is critical for the expression of multiple contributors to tumor growth and invasion. On the basis of preclinical data suggesting synergy of HER2 inhibition and mTOR inhibition in breast and lung cancer models, we conducted a phase I combination study of neratinib, a small-molecule irreversible pan-HER tyrosine kinase inhibitor, and temsirolimus, an mTOR inhibitor, in patients with advanced solid tumors. PATIENTS AND METHODS: This study enrolled patients to dosing combinations of neratinib and temsirolimus. The primary objective was to estimate the toxicity contour of the combination and establish recommended phase II doses. RESULTS: Sixty patients were treated on 12 of 16 possible dosing combinations. Diarrhea was the most common drug-related (93%) and dose-limiting toxicity (DLT), constituting four of 10 DLTs. Dose-limiting grade 3 metabolic abnormalities were also observed. Other frequent drug-related toxicities included nausea, stomatitis (both 53%), and anemia (48%). Two maximum-tolerated dose combinations were identified: 200 mg of neratinib/25 mg of temsirolimus and 160 mg of neratinib/50 mg of temsirolimus. Responses were noted in patients with HER2-amplified breast cancer resistant to trastuzumab, HER2-mutant non-small-cell lung cancer, and tumor types without identified mutations in the HER-PI3K-mTOR pathway. CONCLUSION: The combination of neratinib and temsirolimus was tolerable and demonstrated antitumor activity in multiple tumor types, warranting further evaluation.

Design of oncology clinical trials: a review.

Cancer is a disease that occurs due to the uncontrolled multiplication of cells that invade nearby tissues and can spread to other parts of the body. An increased incidence of cancer in the world has led to an increase in oncology research and in the number of oncology trials. Well designed oncology clinical trials are a key part of developing effective anti-cancer drugs. This review focuses on statistical considerations in the design and analysis of oncology clinical trials.

Integration of cell biology, pharmacological modeling and statistical analysis: part I: cell biology and PK/PD in the Oncology paradigm.

The motivation of this two-part review article is to provide a comprehensive picture of cancer, cancer drugs and the detection and treatment of cancer. In order to do so, this article integrates the cell biology and biophysics of cancer as well as the modeling of preclinical Oncology drug data and statistical analysis of Oncology clinical trials data. It also discusses novel cancer diagnostic tools and standard and potential treatment options.

Phase II trial of temsirolimus in children with high-grade glioma, neuroblastoma and rhabdomyosarcoma.

PURPOSE: A phase II study of temsirolimus was conducted in children and adolescents with high-grade glioma, neuroblastoma or rhabdomyosarcoma. PATIENTS AND METHODS: Temsirolimus 75 mg/m(2) was administered once weekly until disease progression or intolerance. Using the Simon 2-stage design, further enrolment in each disease cohort required ≥ 2 objective responses within the first 12 weeks for the first 12 evaluable patients (those who received ≥ 3 temsirolimus doses). RESULTS: Fifty-two heavily pretreated patients with relapsed (12%) or refractory (88%) disease, median age 8 years (range 1-21 years), were enroled and treated. One patient with neuroblastoma achieved confirmed partial response within the first 12 weeks; thus, none of the 3 cohorts met the criterion for continued enrolment. Disease stabilisation at week 12 was observed in 7 of 17 patients (41%) with high-grade glioma (5 diffuse pontine gliomas, 1 glioblastoma multiforme and 1 anaplastic astrocytoma), 6 of 19 (32%) with neuroblastoma and 1 of 16 (6%) with rhabdomyosarcoma (partial response confirmed at week 18). In the three cohorts, median duration of stable disease or better was 128, 663 and 75 d, respectively. The most common treatment-related adverse events were thrombocytopaenia, hyperlipidaemia and aesthenia. Pharmacokinetic findings were similar to those observed in adults. CONCLUSIONS: Temsirolimus administered weekly at the dose of 75 mg/m(2) did not meet the primary objective efficacy threshold in children with high-grade glioma, neuroblastoma or rhabdomyosarcoma; however, meaningful prolonged stable disease merits further evaluation in combination therapy.

Phase I study of temsirolimus in pediatric patients with recurrent/refractory solid tumors.

PURPOSE: To determine dose-limiting toxicities, maximum-tolerated dose (MTD), pharmacokinetics, and pharmacodynamics of weekly intravenous temsirolimus, a mammalian target of rapamycin (mTOR) signaling pathway inhibitor, in pediatric patients with recurrent or refractory solid tumors. PATIENTS AND METHODS: Cohorts of three to six patients 1 to 21 years of age with recurrent or refractory solid tumors were treated with a 1-hour intravenous infusion of temsirolimus weekly for 3 weeks per course at one of four dose levels: 10, 25, 75, or 150 mg/m(2). During the first two courses, pharmacokinetic and pharmacodynamic evaluations (phosphorylation of S6, AKT, and 4EBP1 in peripheral-blood mononuclear cells) were performed. RESULTS: Dose-limiting toxicity (grade 3 anorexia) occurred in one of 18 evaluable patients at the 150 mg/m(2) level, which was determined to be tolerable, and an MTD was not identified. In 13 patients evaluable for response after two courses of therapy, one had complete response (CR; neuroblastoma) and five had stable disease (SD). Four patients (three SDs + one CR) remained on treatment for more than 4 months. The sum of temsirolimus and sirolimus areas under the concentration-time curve was comparable to values in adults. AKT and 4EBP1 phosphorylation were inhibited at all dose levels, particularly after two courses. CONCLUSION: Weekly intravenous temsirolimus is well tolerated in children with recurrent solid tumors, demonstrates antitumor activity, has pharmacokinetics similar to those in adults, and inhibits the mTOR signaling pathway in peripheral-blood mononuclear cells. Further studies are needed to define the optimal dose for use in combination with other antineoplastic agents in pediatric patients.

Neratinib, an irreversible pan-ErbB receptor tyrosine kinase inhibitor: results of a phase II trial in patients with advanced non-small-cell lung cancer.

PURPOSE: Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have had a significant impact on non-small-cell lung cancer (NSCLC) outcomes, particularly for patients with EGFR mutations. Resistance emerges after 9 to 12 months, primarily mediated by the T790M resistance mutation. We studied neratinib, an irreversible pan-ErbB TKI that may overcome T790M. PATIENTS AND METHODS: Patients with advanced NSCLC underwent EGFR sequencing of available tumor tissue at enrollment. Those with > or = 12 weeks of prior TKI therapy were placed in arm A if they were EGFR mutation positive or arm B if they were wild-type. Arm C included TKI-naïve patients with adenocarcinoma and light smoking histories (< or = 20 pack-years). All patients received daily oral neratinib, initially at 320 mg but subsequently reduced to 240 mg because of excessive diarrhea. The primary end point was objective response rate (RR). RESULTS: One-hundred sixty-seven patients were treated: 91 in arm A, 48 in arm B, and 28 in arm C. Diarrhea was the most common toxicity; grade 3 incidence was 50% at 320 mg but improved to 25% after dose reduction. The RR was 3% in arm A and zero in arms B and C. No patients with known T790M responded. Notably, three of four patients with an exon 18 G719X EGFR mutation had a partial response and the fourth had stable disease lasting 40 weeks. CONCLUSION: Neratinib had low activity in patients with prior benefit from TKIs and in TKI-naïve patients, potentially because of insufficient bioavailability from diarrhea-imposed dose limitation. Responses were seen in patients with the rare G719X EGFR mutation, highlighting the importance of obtaining comprehensive genetic information on trials of targeted agents.

A mitotic kinesin-6, Pav-KLP, mediates interdependent cortical reorganization and spindle dynamics in Drosophila embryos.

We investigated the role of Pav-KLP, a kinesin-6, in the coordination of spindle and cortical dynamics during mitosis in Drosophila embryos. In vitro, Pav-KLP behaves as a dimer. In vivo, it localizes to mitotic spindles and furrows. Inhibition of Pav-KLP causes defects in both spindle dynamics and furrow ingression, as well as causing changes in the distribution of actin and vesicles. Thus, Pav-KLP stabilizes the spindle by crosslinking interpolar microtubule bundles and contributes to actin furrow formation possibly by transporting membrane vesicles, actin and/or actin regulatory molecules along astral microtubules. Modeling suggests that furrow ingression during cellularization depends on: (1) a Pav-KLP-dependent force driving an initial slow stage of ingression; and (2) the subsequent Pav-KLP-driven transport of actin- and membrane-containing vesicles to the furrow during a fast stage of ingression. We hypothesize that Pav-KLP is a multifunctional mitotic motor that contributes both to bundling of interpolar microtubules, thus stabilizing the spindle, and to a biphasic mechanism of furrow ingression by pulling down the furrow and transporting vesicles that deliver new material to the descending furrow.

The forces behind cell movement.

Cell movement is a complex phenomenon primarily driven by the actin network beneath the cell membrane, and can be divided into three general components: protrusion of the leading edge of the cell, adhesion of the leading edge and deadhesion at the cell body and rear, and cytoskeletal contraction to pull the cell forward. Each of these steps is driven by physical forces generated by unique segments of the cytoskeleton. This review examines the specific physics underlying these phases of cell movement and the origins of the forces that drive locomotion.