Lenvatinib plus pembrolizumab for patients with previously treated advanced ovarian cancer: Results from the phase 2 multicohort LEAP-005 study.

OBJECTIVES: The phase 2, multicohort, open-label LEAP-005 study evaluated lenvatinib plus pembrolizumab in patients with previously treated advanced solid tumors. We report outcomes from the ovarian cancer cohort. METHODS: Eligible patients had metastatic/unresectable ovarian cancer and had received 3 previous lines of therapy. Patients received lenvatinib 20 mg/day plus pembrolizumab 200 mg every 3 weeks. Treatment continued until progression, unacceptable toxicity, or (for pembrolizumab) completion of 35 cycles. Primary endpoints were objective response rate (ORR) per RECIST version 1.1 and safety. Secondary endpoints included duration of response (DOR), progression-free survival (PFS), and overall survival (OS). RESULTS: Thirty-one patients were enrolled. 39% had high grade serous ovarian cancer, 23% were platinum-sensitive, 55% were platinum-resistant, 23% were platinum-refractory, and 84% had tumors that had a PD-L1 combined positive (CPS) score ≥1. ORR (95% CI) was 26% (12%-45%) by investigator assessment and 35% (19%-55%) by blinded independent central review (BICR). Per BICR, median DOR was 9.2 (1.5+ to 37.8+) months. ORRs (95% CI) by BICR were 35% (9/26 patients; 17%-56%) for PD-L1 CPS ≥ 1 disease and 50% (2/4 patients; 7%-93%) for PD-L1 CPS < 1 disease. Median (95% CI) PFS by BICR and OS were 6.2 (4.0-8.5) months and 21.3 (11.7-32.3) months, respectively. Treatment-related AEs occurred in 94% of patients (grade 3-4, 77%). One patient died from treatment-related hypovolemic shock. CONCLUSIONS: Lenvatinib plus pembrolizumab demonstrated antitumor activity as fourth line therapy in patients with advanced ovarian cancer, and no unanticipated safety signals were identified. Responses were observed regardless of PD-L1 status.

Lenvatinib Plus Pembrolizumab Versus Sunitinib in First-Line Treatment of Advanced Renal Cell Carcinoma: Final Prespecified Overall Survival Analysis of CLEAR, a Phase III Study.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical trial updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.We present the final prespecified overall survival (OS) analysis of the open-label, phase III CLEAR study in treatment-naïve patients with advanced renal cell carcinoma (aRCC). With an additional follow-up of 23 months from the primary analysis, we report results from the lenvatinib plus pembrolizumab versus sunitinib comparison of CLEAR. Treatment-naïve patients with aRCC were randomly assigned to receive lenvatinib (20 mg orally once daily in 21-day cycles) plus pembrolizumab (200 mg intravenously once every 3 weeks) or sunitinib (50 mg orally once daily [4 weeks on/2 weeks off]). At this data cutoff date (July 31, 2022), the OS hazard ratio (HR) was 0.79 (95% CI, 0.63 to 0.99). The median OS (95% CI) was 53.7 months (95% CI, 48.7 to not estimable [NE]) with lenvatinib plus pembrolizumab versus 54.3 months (95% CI, 40.9 to NE) with sunitinib; 36-month OS rates (95% CI) were 66.4% (95% CI, 61.1 to 71.2) and 60.2% (95% CI, 54.6 to 65.2), respectively. The median progression-free survival (95% CI) was 23.9 months (95% CI, 20.8 to 27.7) with lenvatinib plus pembrolizumab and 9.2 months (95% CI, 6.0 to 11.0) with sunitinib (HR, 0.47 [95% CI, 0.38 to 0.57]). Objective response rate also favored the combination over sunitinib (71.3% v 36.7%; relative risk 1.94 [95% CI, 1.67 to 2.26]). Treatment-emergent adverse events occurred in >90% of patients who received either treatment. In conclusion, lenvatinib plus pembrolizumab achieved consistent, durable benefit with a manageable safety profile in treatment-naïve patients with aRCC.

Characterization and Management of Adverse Reactions in Patients With Advanced Endometrial Cancer Receiving Lenvatinib Plus Pembrolizumab.

BACKGROUND: Lenvatinib plus pembrolizumab significantly improved efficacy compared with chemotherapy in patients with advanced endometrial cancer (aEC) regardless of microsatellite instability status or histologic subtype, who had disease progression following prior platinum-based therapy, in Study-309/KEYNOTE-775. The safety profile of the combination was generally consistent with that of each monotherapy drug and of the combination in patients with endometrial cancer and other solid tumors. Given the medical complexity of patients with aEC, this paper aims to characterize key adverse reactions (ARs) of the combination treatment and review management strategies, providing a guide for AR management to maximize anticancer benefits and minimize treatment discontinuation. MATERIALS AND METHODS: In Study-309/KEYNOTE-775, patients received lenvatinib (20 mg orally once daily) plus pembrolizumab (200 mg intravenously every 3 weeks) or chemotherapy (doxorubicin or paclitaxel). The incidence and median time to the first onset of ARs, dose modifications, and concomitant medications are described. Key ARs characterized include hypothyroidism, hypertension, fatigue, diarrhea, musculoskeletal disorders, nausea, decreased appetite, vomiting, stomatitis, weight decreased, proteinuria, and palmar-plantar erythrodysesthesia syndrome. RESULTS: As expected, the most common any-grade key ARs included: hypothyroidism, hypertension, fatigue, diarrhea, and musculoskeletal disorders. Grades 3-4 key ARs with incidence ≥10% included: hypertension, fatigue, and weight decreased. Key ARs first occurred within approximately 3 months of treatment initiation. AR management strategies consistent with the prescribing information and the study protocol are discussed. CONCLUSION: Successful AR management strategies for lenvatinib plus pembrolizumab include education of the patient and entire treatment team, preventative measures and close monitoring, and judicious use of dose modifications and concomitant medications. CLINICALTRIALS.GOV ID: NCT03517449.

Pembrolizumab with or Without Lenvatinib as First-line Therapy for Patients with Advanced Urothelial Carcinoma (LEAP-011): A Phase 3, Randomized, Double-Blind Trial.

BACKGROUND: Pembrolizumab plus lenvatinib has shown antitumor activity and acceptable safety in patients with platinum-refractory urothelial carcinoma (UC). OBJECTIVE: To evaluate pembrolizumab plus either lenvatinib or placebo as first-line therapy for advanced UC in the phase 3 LEAP-011 study. DESIGN, SETTING, AND PARTICIPANTS: Patients with advanced UC who were ineligible for cisplatin-based therapy or any platinum-based chemotherapy were enrolled. INTERVENTION: Patients were randomly assigned (1:1) to pembrolizumab 200 mg intravenously every 3 wk plus either lenvatinib 20 mg or placebo orally once daily. OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Dual primary endpoints were progression-free survival (PFS) and overall survival (OS). An external data monitoring committee (DMC) regularly reviewed safety and efficacy data every 3 mo. RESULTS AND LIMITATIONS: Between June 25, 2019 and July 21, 2021, 487 patients were allocated to receive lenvatinib plus pembrolizumab (n = 245) or placebo plus pembrolizumab (n = 242). The median time from randomization to the data cutoff date (July 26, 2021) was 12.8 mo (interquartile range, 6.9-19.3). The median PFS was 4.5 mo in the combination arm and 4.0 mo in the pembrolizumab arm (hazard ratio [HR] 0.90 [95% confidence interval {CI} 0.72-1.14]). The median OS was 11.8 mo for the combination arm and 12.9 mo for the pembrolizumab arm (HR 1.14 [95% CI 0.87-1.48]). Grade 3-5 adverse events attributed to trial treatment occurred in 123 of 241 patients (51%) treated with lenvatinib plus pembrolizumab and in 66 of 242 patients (27%) treated with placebo plus pembrolizumab. This trial was terminated earlier than initially planned based on recommendation from the DMC. CONCLUSIONS: The benefit-to-risk ratio for first-line lenvatinib plus pembrolizumab was not considered favorable versus pembrolizumab plus placebo as first-line therapy in patients with advanced UC. PATIENT SUMMARY: Lenvatinib plus pembrolizumab was not more effective than pembrolizumab plus placebo in patients with advanced urothelial carcinoma.

Pembrolizumab With or Without Lenvatinib for First-Line Metastatic NSCLC With Programmed Cell Death-Ligand 1 Tumor Proportion Score of at least 1% (LEAP-007): A Randomized, Double-Blind, Phase 3 Trial.

INTRODUCTION: Lenvatinib plus pembrolizumab was found to have antitumor activity and acceptable safety in previously treated metastatic NSCLC. We evaluated first-line lenvatinib plus pembrolizumab versus placebo plus pembrolizumab in metastatic NSCLC in the LEAP-007 study (NCT03829332/NCT04676412). METHODS: Patients with previously untreated stage IV NSCLC with programmed cell death-ligand 1 tumor proportion score of at least 1% without targetable EGFR/ROS1/ALK aberrations were randomized 1:1 to lenvatinib 20 mg or placebo once daily; all patients received pembrolizumab 200 mg every 3 weeks for up to 35 cycles. Primary end points were progression-free survival (PFS) per Response Evaluation Criteria in Solid Tumors version 1.1 and overall survival (OS). We report results from a prespecified nonbinding futility analysis of OS performed at the fourth independent data and safety monitoring committee review (futility bound: one-sided p < 0.4960). RESULTS: A total of 623 patients were randomized. At median follow-up of 15.9 months, median (95% confidence interval [CI]) OS was 14.1 (11.4‒19.0) months in the lenvatinib plus pembrolizumab group versus 16.4 (12.6‒20.6) months in the placebo plus pembrolizumab group (hazard ratio = 1.10 [95% CI: 0.87‒1.39], p = 0.79744 [futility criterion met]). Median (95% CI) PFS was 6.6 (6.1‒8.2) months versus 4.2 (4.1‒6.2) months, respectively (hazard ratio = 0.78 [95% CI: 0.64‒0.95]). Grade 3 to 5 treatment-related adverse events occurred in 57.9% of patients (179 of 309) versus 24.4% (76 of 312). Per data and safety monitoring committee recommendation, the study was unblinded and lenvatinib and placebo were discontinued. CONCLUSIONS: Lenvatinib plus pembrolizumab did not have a favorable benefit‒risk profile versus placebo plus pembrolizumab. Pembrolizumab monotherapy remains an approved treatment option in many regions for first-line metastatic NSCLC with programmed cell death-ligand 1 tumor proportion score of at least 1% without EGFR/ALK alterations.

Phase 3 CLEAR study in patients with advanced renal cell carcinoma: outcomes in subgroups for the lenvatinib-plus-pembrolizumab and sunitinib arms.

Introduction: The phase 3 CLEAR study demonstrated that lenvatinib plus pembrolizumab significantly improved efficacy versus sunitinib as first-line treatment for patients with advanced renal cell carcinoma (RCC). Prognostic features including presence and/or site of baseline metastases, prior nephrectomy, and sarcomatoid features have been associated with disease and treatment success. This subsequent analysis explores outcomes in patients with or without specific prognostic features. Methods: In CLEAR, patients with clear cell RCC were randomly assigned (1:1:1) to receive either lenvatinib (20 mg/day) plus pembrolizumab (200 mg every 3 weeks), lenvatinib (18 mg/day) plus everolimus (5 mg/day), or sunitinib alone (50 mg/day, 4 weeks on, 2 weeks off). In this report, progression-free survival (PFS), overall survival (OS), and objective response rate (ORR) were all assessed in the lenvatinib-plus-pembrolizumab and the sunitinib arms, based on baseline features: lung metastases, bone metastases, liver metastases, prior nephrectomy, and sarcomatoid histology. Results: In all the assessed subgroups, median PFS was longer with lenvatinib-plus-pembrolizumab than with sunitinib treatment, notably among patients with baseline bone metastases (HR 0.33, 95% CI 0.21-0.52) and patients with sarcomatoid features (HR 0.39, 95% CI 0.18-0.84). Median OS favored lenvatinib plus pembrolizumab over sunitinib irrespective of metastatic lesions at baseline, prior nephrectomy, and sarcomatoid features. Of interest, among patients with baseline bone metastases the HR for survival was 0.50 (95% CI 0.30-0.83) and among patients with sarcomatoid features the HR for survival was 0.91 (95% CI 0.32-2.58); though for many groups, median OS was not reached. ORR also favored lenvatinib plus pembrolizumab over sunitinib across all subgroups; similarly, complete responses also followed this pattern. Conclusion: Efficacy outcomes improved following treatment with lenvatinib-plus-pembrolizumab versus sunitinib in patients with RCC-irrespective of the presence or absence of baseline lung metastases, baseline bone metastases, baseline liver metastases, prior nephrectomy, or sarcomatoid features. These findings corroborate those of the primary CLEAR study analysis in the overall population and support lenvatinib plus pembrolizumab as a standard of care in 1L treatment for patients with advanced RCC. Clinical trial registration: ClinicalTrials.gov, identifier NCT02811861.

Corrigendum: Phase 3 CLEAR study in patients with advanced renal cell carcinoma: outcomes in subgroups for the lenvatinib-plus-pembrolizumab and sunitinib arms.

[This corrects the article DOI: 10.3389/fonc.2023.1223282.].

Paediatric Strategy Forum for medicinal product development of multi-targeted kinase inhibitors in bone sarcomas: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration.

The eighth Paediatric Strategy Forum focused on multi-targeted kinase inhibitors (mTKIs) in osteosarcoma and Ewing sarcoma. The development of curative, innovative products in these tumours is a high priority and addresses unmet needs in children, adolescents and adults. Despite clinical and investigational use of mTKIs, efficacy in patients with bone tumours has not been definitively demonstrated. Randomised studies, currently being planned or in progress, in front-line and relapse settings will inform the further development of this class of product. It is crucial that these are rapidly initiated to generate robust data to support international collaborative efforts. The experience to date has generally indicated that the safety profile of mTKIs as monotherapy, and in combination with chemotherapy or other targeted therapy, is consistent with that of adults and that toxicity is manageable. Increasing understanding of relevant predictive biomarkers and tumour biology is absolutely critical to further develop this class of products. Biospecimen samples for correlative studies and biomarker development should be shared, and a joint academic-industry consortium created. This would result in an integrated collection of serial tumour tissues and a systematic retrospective and prospective analyses of these samples to ensure robust assessment of biologic effect of mTKIs. To support access for children to benefit from these novel therapies, clinical trials should be designed with sufficient scientific rationale to support regulatory and payer requirements. To achieve this, early dialogue between academia, industry, regulators, and patient advocates is essential. Evaluating feasibility of combination strategies and then undertaking a randomised trial in the same protocol accelerates drug development. Where possible, clinical trials and development should include children, adolescents, and adults less than 40 years. To respond to emerging science, in approximately 12 months, a multi-stakeholder group will meet and review available data to determine future directions and priorities.

Lenvatinib dose, efficacy, and safety in the treatment of multiple malignancies.

INTRODUCTION: Lenvatinib is an oral multitargeted tyrosine kinase inhibitor that has shown efficacy and manageable safety across multiple cancer types. The recommended starting doses for lenvatinib differ across cancer types and indications based on whether it is used as monotherapy or as combination therapy. AREAS COVERED: This review covers clinical trials that established the dosing paradigm and efficacy of lenvatinib and defined its adverse-event profile as a monotherapy; or in combination with the mTOR inhibitor, everolimus; or the anti-PD-1 antibody, pembrolizumab; and/or chemotherapy. EXPERT OPINION: Lenvatinib has been established as standard-of-care either as a monotherapy or in combination with other anticancer agents for the treatment of radioiodine-refractory differentiated thyroid carcinoma, hepatocellular carcinoma, renal cell carcinoma, and endometrial carcinoma, and is being investigated further across several other tumor types. The dosing and adverse-event management strategies for lenvatinib have been developed through extensive clinical trial experience. Collectively, the data provide the rationale to start lenvatinib at the recommended doses and then interrupt or dose reduce as necessary to achieve required dose intensity for maximized patient benefit. The adverse-event profile of lenvatinib is consistent with that of other tyrosine kinase inhibitors, and clinicians are encouraged to review and adopt relevant symptom-management strategies.

OLIE, ITCC-082: a Phase II trial of lenvatinib plus ifosfamide and etoposide in relapsed/refractory osteosarcoma.

While survival rates for patients with relapsed/refractory osteosarcoma are low, kinase inhibitors have shown efficacy in its treatment. The multikinase inhibitor lenvatinib, plus ifosfamide and etoposide, showed antitumor activity in a Phase II study in patients with relapsed/refractory osteosarcoma. This Phase II randomized controlled trial (OLIE) will assess whether the combination of lenvatinib + ifosfamide + etoposide is superior to ifosfamide + etoposide alone in children, adolescents and young adults with relapsed/refractory osteosarcoma. The primary end point is progression-free survival; secondary and exploratory end points include, but are not limited to, overall survival, objective response rate, safety and tolerability, pharmacokinetic characterization of lenvatinib in the combination treatment, quality of life and quantification of baseline unresectable lesions that are converted to resectable.

Lay abstract Traditional treatment for osteosarcoma (bone cancer) includes drugs that cause cell damage, such as ifosfamide and etoposide. The study in this article looked at adding lenvatinib, a drug that works to block development of blood vessels, to traditional chemotherapy to see whether it worked better. 'OLIE' is a Phase II clinical study comparing lenvatinib + chemotherapy (ifosfamide + etoposide) to the chemotherapy alone (ifosfamide + etoposide). An earlier study indicated that this drug combination may be successful. The study includes children, adolescents and young adults with osteosarcoma that has come back after, or did not respond to, previous treatment. OLIE will look at the antitumor activity and the side effects of this drug combination. The OLIE study is currently enrolling patients worldwide. Clinical trial registration number: NCT04154189 (ClinicalTrials.gov).

Lenvatinib with etoposide plus ifosfamide in patients with refractory or relapsed osteosarcoma (ITCC-050): a multicentre, open-label, multicohort, phase 1/2 study.

BACKGROUND: Tyrosine kinase inhibitors have shown activity in osteosarcoma and might enhance the efficacy of chemotherapy. We aimed to determine the recommended phase 2 dose and antitumour activity of lenvatinib with etoposide plus ifosfamide in patients with refractory or relapsed osteosarcoma. METHODS: This multicentre, open-label, multicohort, phase 1/2 trial was done at 17 hospitals in six countries. Eligible patients were aged 2-25 years, had relapsed or refractory osteosarcoma, measurable or evaluable disease per Response Evaluation Criteria in Solid Tumors version 1.1, Lansky play-performance score or Karnofsky performance score of 50% or higher, up to one previous VEGF or VEGF receptor-targeted therapy, and a life expectancy of at least 3 months. This study includes a combination dose-finding phase 1 part (cohort 3A) and a phase 2 combination expansion in patients with osteosarcoma (cohort 3B). Lenvatinib was administered orally at a starting dose of 11 mg/m2 per day, capped at 24 mg per day, and etoposide (100 mg/m2 per day) plus ifosfamide (3000 mg/m2 per day) were administered intravenously on days 1-3 of each 21-day cycle for a maximum of five cycles. Lenvatinib monotherapy continued after these five cycles until disease progression, toxic effects, or patient choice to discontinue. The phase 1 primary endpoint was to determine the recommended phase 2 dose by evaluating dose-limiting toxicity and the phase 2 primary endpoint was progression-free survival at 4 months. Progression-free survival was measured in the full analysis set, which included all patients enrolled for efficacy outcomes; safety was assessed in all patients who received any study drug. This study is registered with ClinicalTrials.gov, NCT02432274. FINDINGS: 30 patients were screened for enrolment into cohort 3A between May 9, 2016, and June 3, 2019, and 22 patients for enrolment into cohort 3B between Sept 13, 2018, and July 18, 2019. Eight patients from cohort 3A and two from cohort 3B were ineligible for enrolment in the study. In phase 1, dose-limiting toxicities were observed in three patients (one in the lenvatinib 11 mg/m2 combination group and two in the 14 mg/m2 combination group) and the recommended phase 2 dose was determined as lenvatinib 14 mg/m2 per day (with daily dose cap of 24 mg) and etoposide 100 mg/m2 per day plus ifosfamide 3000 mg/m2 per day administered intravenously on days 1-3 of each 21-day cycle for a maximum of five cycles. 35 patients from phase 1 (cohort 3A; n=15) and phase 2 (cohort 3B; n=20) were treated at the recommended phase 2 dose and their results were pooled. Progression-free survival at 4 months was 51% (95% CI 34-69) in 18 of 35 patients per the binomial estimate. The most common grade 3-4 treatment-emergent adverse events were neutropenia (27 [77%] of 35), thrombocytopenia (25 [71%]), anaemia (19 [54%]), and decreased white blood cell count (19 [54%]). 26 [74%] of 35 patients had serious treatment-emergent adverse events and no treatment-related deaths occurred. INTERPRETATION: Lenvatinib with etoposide plus ifosfamide shows promising antitumour activity with no new safety signals in patients with refractory and relapsed osteosarcoma. These findings warrant further investigation in an ongoing randomised phase 2 study (NCT04154189). FUNDING: Eisai and Merck Sharp & Dohme.

Lenvatinib plus pembrolizumab in patients with either treatment-naive or previously treated metastatic renal cell carcinoma (Study 111/KEYNOTE-146): a phase 1b/2 study.

BACKGROUND: Despite advances in the first-line treatment of metastatic renal cell carcinoma (RCC), there is an unmet need for options to address disease progression during or after treatment with immune checkpoint inhibitors (ICIs). Pembrolizumab and lenvatinib are active as monotherapies in RCC; thus, we aimed to evaluate the combination of lenvatinib plus pembrolizumab in these patients. METHODS: We report results of the metastatic RCC cohort from an open-label phase 1b/2 study of lenvatinib plus pembrolizumab in patients aged at least 18 years with selected solid tumours and an Eastern Cooperative Oncology Group performance status of 0-1. Oral lenvatinib at 20 mg was given once daily along with intravenous pembrolizumab at 200 mg once every 3 weeks. Patients remained on study drug treatment until disease progression, development of unacceptable toxicity, or withdrawal of consent. Efficacy was analysed in patients with clear cell metastatic RCC receiving study drug by previous therapy grouping: treatment naive, previously treated ICI naive (previously treated with at least one line of therapy but not with an anti-PD-1 or anti-PD-L1 ICI), and ICI pretreated (ie, anti-PD-1 or anti-PD-L1) patients. Safety was analysed in all enrolled and treated patients. The primary endpoint was the objective response rate at week 24 per immune-related Response Evaluation Criteria In Solid Tumors (irRECIST) by investigator assessment. This trial is registered with ClinicalTrials.gov (NCT02501096) and with the EU Clinical Trials Register (EudraCT2017-000300-26), and is closed to new participants. FINDINGS: Between July 21, 2015, and Oct 16, 2019, 145 patients were enrolled in the study. Two patients had non-clear cell RCC and were excluded from the efficacy analysis (one in the treatment-naive group and one in the ICI-pretreated group); thus, the population evaluated for efficacy comprised 143 patients (n=22 in the treatment-naive group, n=17 in the previously treated ICI-naive group, and n=104 in the ICI-pretreated group). All 145 enrolled patients were included in the safety analysis. The median follow-up was 19·8 months (IQR 14·3-28·4). The number of patients with an objective response at week 24 by irRECIST was 16 (72·7%, 95% CI 49·8-89·3) of 22 treatment-naive patients, seven (41·2%, 18·4-67·1) of 17 previously treated ICI-naive patients, and 58 (55·8%, 45·7-65·5) of 104 ICI-pretreated patients. Of 145 patients, 82 (57%) had grade 3 treatment-related adverse events and ten (7%) had grade 4 treatment-related adverse events. The most common grade 3 treatment-related adverse event was hypertension (30 [21%] of 145 patients). Treatment-related serious adverse events occurred in 36 (25%) patients, and there were three treatment-related deaths (upper gastrointestinal haemorrhage, sudden death, and pneumonia). INTERPRETATION: Lenvatinib plus pembrolizumab showed encouraging antitumour activity and a manageable safety profile and might be an option for post-ICI treatment of metastatic RCC. FUNDING: Eisai and Merck Sharp & Dohme.

Positively selected modifications in the pore of TbAQP2 allow pentamidine to enter Trypanosoma brucei.

Mutations in the Trypanosoma brucei aquaporin AQP2 are associated with resistance to pentamidine and melarsoprol. We show that TbAQP2 but not TbAQP3 was positively selected for increased pore size from a common ancestor aquaporin. We demonstrate that TbAQP2's unique architecture permits pentamidine permeation through its central pore and show how specific mutations in highly conserved motifs affect drug permeation. Introduction of key TbAQP2 amino acids into TbAQP3 renders the latter permeable to pentamidine. Molecular dynamics demonstrates that permeation by dicationic pentamidine is energetically favourable in TbAQP2, driven by the membrane potential, although aquaporins are normally strictly impermeable for ionic species. We also identify the structural determinants that make pentamidine a permeant although most other diamidine drugs are excluded. Our results have wide-ranging implications for optimising antitrypanosomal drugs and averting cross-resistance. Moreover, these new insights in aquaporin permeation may allow the pharmacological exploitation of other members of this ubiquitous gene family.

African sleeping sickness is a potentially deadly illness caused by the parasite Trypanosoma brucei. The disease is treatable, but many of the current treatments are old and are becoming increasingly ineffective. For instance, resistance is growing against pentamidine, a drug used in the early stages in the disease, as well as against melarsoprol, which is deployed when the infection has progressed to the brain. Usually, cases resistant to pentamidine are also resistant to melarsoprol, but it is still unclear why, as the drugs are chemically unrelated. Studies have shown that changes in a water channel called aquaglyceroporin 2 (TbAQP2) contribute to drug resistance in African sleeping sickness; this suggests that it plays a role in allowing drugs to kill the parasite. This molecular 'drain pipe' extends through the surface of T. brucei, and should allow only water and a molecule called glycerol in and out of the cell. In particular, the channel should be too narrow to allow pentamidine or melarsoprol to pass through. One possibility is that, in T. brucei, the TbAQP2 channel is abnormally wide compared to other members of its family. Alternatively, pentamidine and melarsoprol may only bind to TbAQP2, and then 'hitch a ride' when the protein is taken into the parasite as part of the natural cycle of surface protein replacement. Alghamdi et al. aimed to tease out these hypotheses. Computer models of the structure of the protein were paired with engineered changes in the key areas of the channel to show that, in T. brucei, TbAQP2 provides a much broader gateway into the cell than observed for similar proteins. In addition, genetic analysis showed that this version of TbAQP2 has been actively selected for during the evolution process of T. brucei. This suggests that the parasite somehow benefits from this wider aquaglyceroporin variant. This is a new resistance mechanism, and it is possible that aquaglyceroporins are also larger than expected in other infectious microbes. The work by Alghamdi et al. therefore provides insight into how other germs may become resistant to drugs.