Biogen

Duchenne muscular dystrophy (DMD), a rare pediatric disease, presents numerous challenges when designing clinical trials, mainly due to the scarcity of available trial participants and the heterogeneity of disease progression. A quantitative clinical trial simulator (CTS) has been developed based on previously published five disease progression models describing each of the longitudinal changes in the velocity at which individuals can complete specified timed functional tests, frequently used as clinical trial efficacy endpoints (supine‐stand, 4‐stair climb, and 10 m walk/run test or 30‐foot walk/run test), as well as each of the longitudinal changes in forced vital capacity and North Star Ambulatory Assessment total score. The model‐based CTS allows researchers to optimize the selection of numerous trial parameters for designing trials for the five functional measures commonly used as endpoints in DMD clinical trials. This case report serves as a demonstration of the tool's functionality while providing an easy‐to‐follow guide for users to reference when preparing simulations of their own design. Two case studies, using input selection based on previous DMD clinical trials, provide realistic examples of how the tool can help optimize clinical trial design without the risk of decreasing statistical significance. This optimization allows researchers to mitigate the risk of designing trials that may be longer, larger, or more inclusive/exclusive than necessary.

Background The hazard ratio of the Cox proportional hazards model is widely used in randomized controlled trials to assess treatment effects. However, two properties of the hazard ratio including the non-collapsibility and built-in selection bias need to be further investigated. Methods We conduct simulations to differentiate the non-collapsibility effect and built-in selection bias from the difference between the marginal and the conditional hazard ratio. Meanwhile, we explore the performance of the Cox model with inverse probability of treatment weighting for covariate adjustment when estimating the marginal hazard ratio. The built-in selection bias is further assessed in the period-specific hazard ratio. Results The conditional hazard ratio is a biased estimate of the marginal effect due to the non-collapsibility property. In contrast, the hazard ratio estimated from the inverse probability of treatment weighting Cox model provides an unbiased estimate of the true marginal hazard ratio. The built-in selection bias only manifests in the period-specific hazard ratios even when the proportional hazards assumption is satisfied. The Cox model with inverse probability of treatment weighting can be used to account for confounding bias and provide an unbiased effect under the randomized controlled trials setting when the parameter of interest is the marginal effect. Conclusions We propose that the period-specific hazard ratios should always be avoided due to the profound effects of built-in selection bias.

The Alzheimer's disease (AD) research community continues to make great strides in expanding approaches for early detection and treatment of the disease, including recent advances in our understanding of fundamental AD pathophysiology beyond the classical targets: beta‐amyloid and tau. Recent clinical trial readouts implicate a variety of non‐amyloid/non‐tau (NANT) approaches that show promise in slowing cognitive decline for people with AD. The Alzheimer's Association Research Roundtable (AARR) meeting held on December 13–14, 2022, reviewed the current state of NANT targets on underlying AD pathophysiology and their contribution to cognitive decline, the current data on a diverse range of NANT biomarkers and therapeutic targets, and the integration of NANT concepts in clinical trial designs. Participants also discussed the current definition of therapies that target underlying AD pathophysiology, what endpoints best define what is considered a meaningful change beyond the current approved definition for clinical efficacy, and how the recent NANT findings should inform the development of future guidelines for AD classification and personalized treatment strategies. Highlights The Alzheimer's Association Research Roundtable (AARR) convened leaders from industry, academia, and government to review the current state of non‐beta amyloid and non‐tau (NANT) targets on underlying Alzheimer's disease (AD) pathophysiology. The totality of scientific and clinical evidence supports the hypothesis that emerging NANT targets play a role in cognitive decline and neurodegeneration in AD. New biomarkers based on NANT targets must be globally developed and implemented with specific consideration of fluid biomarkers as a cost‐effective clinical option, to ensure better, more equitable treatment options for AD.

Real-world studies in the USA report that 41–56% of patients with multiple sclerosis (MS) are ≥ 50 years old, yet data on their response to disease-modifying therapies (DMTs) is limited. Dimethyl fumarate (DMF) is an oral DMT approved for treating relapsing MS. This analysis evaluated the safety, efficacy, and immunophenotype changes of DMF in patients ≥ 50 years compared with patients < 50 years. ESTEEM, a 5-year, real-world, observational phase 4 study, assessed the safety and effectiveness of DMF, including treatment-emergent serious adverse events (SAEs) and adverse events (AEs) leading to treatment discontinuation. Absolute lymphocyte counts (ALCs) were recorded from a subset of patients. The PROCLAIM study, a phase 3b interventional study, reported safety outcomes and lymphocyte subset changes in patients with relapsing–remitting MS (RRMS) treated with DMF. The study evaluated safety outcomes by analyzing the incidence of SAEs and detailed changes in CD4+ and CD8+ T cell compartments over 96 weeks of DMF treatment. ESTEEM included 4020 patients aged < 50 years and 1069 aged ≥ 50 years. AEs leading to discontinuation were reported by 19.6% patients < 50 years and 29.6% of patients ≥ 50 years, with gastrointestinal disorders being the most common. SAEs were reported by 5.2% of patients < 50 years and 8.9% those ≥ 50 years. In PROCLAIM, SAEs were reported in 13% of patients < 50 years and 10% of those ≥ 50 years. Median ALC decreased by 35% in patients < 50 years and 50% in those ≥ 50 years in ESTEEM, with similar patterns observed in PROCLAIM. ESTEEM found no unexpected safety signals in older patients and annualized relapse rates (ARRs) were significantly reduced in both age groups. Both studies indicated that DMF is efficacious and has a favorable safety profile in patients with RRMS aged ≥ 50 years. ESTEEM (NCT02047097), PROCLAIM (NCT02525874).

To elucidate the specific and shared genetic background of schizophrenia (SCZ) and bipolar disorder (BPD), this study explored the association of polygenic liabilities for SCZ and BPD with educational attainment and cognitive aging. Among 106,806 unrelated community participants from the Taiwan Biobank, we calculated the polygenic risk score (PRS) for SCZ (PRSSCZ) and BPD (PRSBPD), shared PRS between SCZ and BPD (PRSSCZ+BPD), and SCZ-specific PRS (PRSSCZvsBPD). Based on the sign-concordance of the susceptibility variants with SCZ/BPD, PRSSCZ was split into PRSSCZ_concordant/PRSSCZ_discordant, and PRSBPD was split into PRSBPD_concordant/PRSBPD_discordant. Ordinal logistic regression models were used to estimate the association with educational attainment. Linear regression models were used to estimate the associations with cognitive aging (n = 27,005), measured by the Mini-Mental State Examination (MMSE), and with MMSE change (n = 6194 with mean follow-up duration of 3.9 y) in individuals aged≥ 60 years. PRSSCZ, PRSBPD, and PRSSCZ+BPD were positively associated with educational attainment, whereas PRSSCZvsBPD was negatively associated with educational attainment. PRSSCZ was negatively associated with MMSE, while PRSBPD was positively associated with MMSE. The concordant and discordant parts of polygenic liabilities have contrasting association, PRSSCZ_concordant and PRSBPD_concordant mainly determined these effects mentioned above. PRSSCZvsBPD predicted decreases in the MMSE scores. Using a large collection of community samples, this study provided evidence for the contrasting effects of polygenic architecture in SCZ and BPD on educational attainment and cognitive aging and suggested that SCZ and BPD were not genetically homogeneous.

Monoclonal antibodies (mAbs) are a major class of biopharmaceuticals manufactured by well‐established processes using Chinese Hamster Ovary (CHO) cells. Next‐generation biomanufacturing using alternative hosts like Komagataella phaffii could improve the accessibility of these medicines, address broad societal goals for sustainability, and offer financial advantages for accelerated development of new products. Antibodies produced by K. phaffii, however, may manifest unique molecular quality attributes, like host‐dependent, product‐related variants, that could raise potential concerns for clinical use. We demonstrate here conservative modifications to the amino acid sequence of aglycosylated antibodies based on the human IgG1 isotype that minimize product‐related variations when secreted by K. phaffii. A combination of 2–3 changes of amino acids reduced variations across six different aglycosylated versions of commercial mAbs. Expression of a modified sequence of NIST mAb in both K. phaffii and CHO cells showed comparable biophysical properties and molecular variations. These results suggest a path toward the production of high‐quality mAbs that could be expressed interchangeably by either yeast or mammalian cells. Improving molecular designs of proteins to enable a range of manufacturing strategies for well‐characterized biopharmaceuticals could accelerate global accessibility and innovations.

Background: Outcomes-based agreements (OBAs) are agreements between payers and manufacturers in which payment for medications is tied to patient outcomes. These contracts aim to measure the value of prescription medications on predefined clinical indicators in real-world patient populations. OBAs are gaining traction in the United States as the health care industry shifts from volume-based to value-based care. Multiple sclerosis (MS) is an appealing therapeutic area for OBAs because of its prevalence, high cost of medications, and multiple effective therapeutic options. Objective: To describe findings from an OBA that was prospectively conducted in a large regional health system for patients with MS taking interferon β-1a or dimethyl fumarate. Methods: In this prospective real-world analysis, commercial or health insurance exchange members were included based on the parameters of the OBA. Disability progression was assessed using a patient-reported outcome, patient-determined disease steps (PDDS). In the OBA, members aged 18 years or older with an MS diagnosis were included in the contract. A baseline score was collected for eligible members, with follow-up scores occurring between a 90-day and 180-day postbaseline score. If a follow-up score was greater than the baseline score, a subsequent PDDS score was collected between 90-days and 120-days to determine if the PDDS score remained elevated, indicating that the member had disability progression. Results: During the contract period, 410 patients were eligible for PDDS collection, with 241 and 169 patients in the dimethyl fumarate and interferon β-1a cohorts, respectively. There were 162 patients who were lost to follow-up, and 64 patients who were ineligible per contract parameters. Of the remaining 184 eligible patients (107 on dimethyl fumarate and 77 on interferon β-1a), 21 (11%) patients had confirmed disability progression (6 on dimethyl fumarate [5.6%] and 15 on interferon β-1a [19.5%]). Conclusions: Our findings suggest that meaningful patient-reported outcomes, such as disability progression, can be operationalized in an innovative OBA.

Background: People living with ALS (plwALS) experience motor control loss, speech/swallowing difficulties, respiratory insufficiency, and early death. Advancing disease stage is typically associated with a greater burden on the health care system, and delays in diagnosis can result in substantial health care resource utilization (HCRU). Objective: To estimate HCRU and cost burden of plwALS across disease stages from a US payer perspective we assessed HCRU and costs in early-, mid-, and late-stage ALS. Methods: Using insurance claims data from the IBM MarketScan Databases between January 2013 and December 2019, we identified plwALS as having at least 2 claims at least 27 days apart with an ALS International Classification of Diseases, Ninth or Tenth Revision diagnosis code (335.20/G12.21) or at least 1 ALS diagnosis code and prescription filled for riluzole/edaravone. Eligible plwALS were aged at least 18 years and had at least 12 months of enrollment data before and at least 6 months after the index date (date diagnosis criteria met). plwALS were grouped into disease stages using an ALS severity-based staging algorithm developed using ALS symptom and staging survey data from 142 neurologists reporting on 880 plwALS. The starting date of each severity stage was defined as the first date of an ALS symptom within the early-, mid-, and late-stage categories, respectively. The ending date for a severity stage was defined as the day before the first date of an ALS symptom from a more severe category. plwALS could transition to more severe stages, with reverse transition of severity excluded. Mixed regression modeling was used to assess differences in HCRU and costs per person-year between severity stages, adjusted for age and sex. Results: 2,273 plwALS were included in the total ALS study sample, with 1,215 early-stage, 1,511 midstage, and 1,186 late-stage plwALS. 90% of early-stage plwALS had ALS symptoms before diagnosis, and 27% of late-stage plwALS had a late-stage symptom before diagnosis. In the evaluation period, later-stage ALS groups had more overall hospital admissions (early = 0.15, middle = 0.23, and late = 0.74; P < 0.01), outpatient visits/service (early = 26.81, middle = 32.78, and late = 48.54; P < 0.01), emergency department visits (early = 0.46, middle = 0.69, and late = 1.03; P < 0.01), and total prescription count (early = 9.23, middle = 11.37, and late = 12.72; P < 0.01) over 12 months. Annualized costs increased as ALS progressed (early = $31,411, middle =$51,481, and late = $121,903; P < 0.01), which was primarily driven by higher frequency of and cost per hospital admission. Conclusions: HCRU and costs increased with ALS progression, with diagnosis frequently occurring even after experiencing late-stage symptoms. These findings highlight the potential value of delaying progression into a more resource-intensive stage by diagnosing and adequately treating plwALS earlier in the disease course.

Hyperphosphorylated TDP-43 aggregates in the cytoplasm of motor neurons is a neuropathological signature of amyotrophic lateral sclerosis (ALS). These aggregates have been proposed to possess a toxic disease driving role in ALS pathogenesis and progression, however, the contribution of phosphorylation to TDP-43 aggregation and ALS disease mechanisms remains poorly understood. We’ve previously shown that CK1δ and CK1ε phosphorylate TDP-43 at disease relevant sites, and that genetic reduction and chemical inhibition could reduce phosphorylated TDP-43 (pTDP-43) levels in cellular models. In this study, we advanced our findings into the hTDP-43-ΔNLS in vivo mouse model of ALS and TDP-43 proteinopathy. This mouse model possesses robust disease-relevant features of ALS, including TDP-43 nuclear depletion, cytoplasmic pTDP-43 accumulation, motor behavior deficits, and shortened survival. We tested the effect of homozygous genetic deletion of Csnk1e in the hTDP-43-ΔNLS mouse model and observed a delay in the formation of pTDP-43 without significant ultimate rescue of TDP-43 proteinopathy or disease progression. Homozygous genetic deletion of Csnk1d is lethal in mice, and we were unable to test the role of CK1δ alone. We then targeted both CK1δ and CK1ε kinases by way of CK1δ/ε-selective PF-05236216 inhibitor in the hTDP-43-ΔNLS mouse model, reasoning that inhibiting CK1ε alone would be insufficient as shown by our Csnk1e knockout mouse model study. Treated mice demonstrated reduced TDP-43 phosphorylation, lowered Nf-L levels, and improved survival in the intermediate stages. The soluble TDP-43 may have been more amenable to the inhibitor treatment than insoluble TDP-43. However, the treatments did not result in improved functional measurements or in overall survival. Our results demonstrate that phosphorylation contributes to neuronal toxicity and suggest CK1δ/ε inhibition in combination with other therapies targeting TDP-43 pathology could potentially provide therapeutic benefit in ALS.

Diagnosing Alzheimer's disease (AD) poses significant challenges to health care, often resulting in delayed or inadequate patient care. The clinical integration of blood‐based biomarkers (BBMs) for AD holds promise in enabling early detection of pathology and timely intervention. However, several critical considerations, such as the lack of consistent guidelines for assessing cognition, limited understanding of BBM test characteristics, insufficient evidence on BBM performance across diverse populations, and the ethical management of test results, must be addressed for widespread clinical implementation of BBMs in the United States. The Global CEO Initiative on Alzheimer's Disease BBM Workgroup convened to address these challenges and provide recommendations that underscore the importance of evidence‐based guidelines, improved training for health‐care professionals, patient empowerment through informed decision making, and the necessity of community‐based studies to understand BBM performance in real‐world populations. Multi‐stakeholder engagement is essential to implement these recommendations and ensure credible guidance and education are accessible to all stakeholders.

Blood‐based biomarkers (BBM) for Alzheimer's disease (AD) are being increasingly used in clinical practice to support an AD diagnosis. In contrast to traditional diagnostic modalities, such as amyloid positron emission tomography and cerebrospinal fluid biomarkers, BBMs offer a more accessible and lower cost alternative for AD biomarker testing. Their unique scalability addresses the anticipated surge in demand for biomarker testing with the emergence of disease‐modifying treatments (DMTs) that require confirmation of amyloid pathology. To facilitate the uptake of BBMs in clinical practice, The Global CEO Initiative on Alzheimer's Disease convened a BBM Workgroup to provide recommendations for two clinical implementational pathways for BBMs: one for current use for triaging and another for future use to confirm amyloid pathology. These pathways provide a standardized diagnostic approach with guidance on interpreting BBM test results. Integrating BBMs into clinical practice will simplify the diagnostic process and facilitate timely access to DMTs for eligible patients.

The Neuronal alpha-Synuclein Disease (NSD) biological definition and Integrated Staging System (NSD-ISS) provide a research framework to identify individuals with Lewy body pathology and stage them based on underlying biology and increasing degree of functional impairment. Utilizing data from the PPMI, PASADENA, and SPARK studies, we developed and applied biologic and clinical data-informed definitions for the NSD-ISS across the disease continuum. Individuals enrolled as Parkinson’s disease, Prodromal, or Healthy Controls were defined and staged based on biological, clinical, and functional anchors at baseline. Across the three studies 1741 participants had SAA data and of these 1030 (59%) were S+ consistent with NSD. Among sporadic PD, 683/736 (93%) were NSD, and the distribution for Stages 2B, 3, and 4 was 25%, 63%, and 9%, respectively. Median (95% CI) time to developing a clinically meaningful outcome was 8.3 (6.2, 10.1), 5.9 (4.1, 6.0), and 2.4 (1.0, 4.0) years for baseline stage 2B, 3, and 4, respectively. We propose pilot biologic and clinical anchors for NSD-ISS. Our results highlight the baseline heterogeneity of individuals currently defined as early PD. Baseline stage predicts time to progression to clinically meaningful milestones. Further research on validation of the anchors in longitudinal cohorts is necessary.

The tauopathies are defined by pathological tau protein aggregates within a spectrum of clinically heterogeneous neurodegenerative diseases. The primary tauopathies meet the definition of rare diseases in the United States. There is no approved treatment for primary tauopathies. In this context, designing the most efficient development programs to translate promising targets and treatments from preclinical studies to early‐phase clinical trials is vital. In September 2022, the Rainwater Charitable Foundation convened an international expert workshop focused on the translation of tauopathy therapeutics through early‐phase trials. Our report on the workshop recommends a framework for principled drug development and a companion lexicon to facilitate communication focusing on reproducibility and achieving common elements. Topics include the selection of targets, drugs, biomarkers, participants, and study designs. The maturation of pharmacodynamic biomarkers to demonstrate target engagement and surrogate disease biomarkers is a crucial unmet need. Highlights Experts provided a framework to translate therapeutics (discovery to clinical trials). Experts focused on the “5 Rights” (target, drug, biomarker, participants, trial). Current research on frontotemporal degeneration, progressive supranuclear palsy, and corticobasal syndrome therapeutics includes 32 trials (37% on biologics) Tau therapeutics are being tested in Alzheimer's disease; primary tauopathies have a large unmet need.

The emergence of the United States Food and Drug Administration (FDA)‐approved amyloid‐targeting therapies for Alzheimer's disease challenges clinicians and healthcare providers with a transformative landscape. Effectively communicating the risks, benefits, burdens, costs, and available support associated with these novel disease‐modifying treatments to patients, families, and other healthcare providers is essential but complex. In response, the Alzheimer's Association's Clinical Meaningfulness Workgroup has proposed language surrounding treatment eligibility, benefits, amyloid‐related imaging abnormalities (ARIA), apolipoprotein E (APOE) genotyping, and treatment costs, serving as a resource to healthcare professionals in navigating discussions with patients and their families. As the landscape evolves with the approval of new Alzheimer's therapies, this resource stands poised for updates, ensuring its continued relevance in facilitating informed and meaningful patient‐provider dialogues. Highlights Effective communication of risks, benefits, burdens, and costs of FDA‐approved amyloid‐targeting antibodies is essential to patients, families, and healthcare providers. The Alzheimer's Association's Clinical Meaningfulness Workgroup provides language for physicians and healthcare providers around treatment eligibility, benefits, ARIA, APOE genotyping, and treatment costs. This supplementary resource may be updated as new AD therapies become approved.

Rationale Zuranolone is an oral positive allosteric modulator of GABAA receptors. Due to its central nervous system (CNS) activity, zuranolone may impact activities requiring complex cognition, including driving. Objective Evaluate the effect of zuranolone on simulated driving performance. Methods In this randomized, double-blind, active- and placebo-controlled, four-period crossover study, treatments included once-nightly zuranolone 50 mg on days 1–7, zuranolone 50 mg on days 1–6 and zuranolone 100 mg on day 7, zopiclone 7.5 mg on days 1 and 7, and placebo on days 1–7. Driving was assessed using a validated simulator. Primary endpoint was standard deviation of lateral position (SDLP), evaluated 9 h post-dose on days 2 and 8. Secondary endpoints included additional driving assessments, cognitive tests, pharmacokinetics, and safety. Results Healthy adults (N = 67) enrolled and received ≥ 1 dose. Zuranolone 50 mg increased SDLP versus placebo on days 2 (least squares mean difference [LSMD]: 7.4 cm; p < 0.0001) and 8 (LSMD: 4.6 cm; p = 0.0106). Zuranolone 100 mg evoked a larger increase in SDLP versus placebo on day 8 (LSMD 18.9 cm; p < 0.0001). Reduced performance in other driving assessments and cognition were observed with zuranolone 50 mg on day 2; many resolved by day 8. Despite the SDLP observations, most participants judged themselves capable of driving. Frequent adverse events (≥ 20%) were CNS-related; most were mild/moderate. Conclusion Zuranolone impaired simulated driving and reduced cognitive function versus placebo 9 h after administration. Although many impairments resolved after 7 days of dosing, driving remained impaired. These results may inform prescriber decision-making.

Omaveloxolone is a nuclear factor (erythroid‐derived 2)‐like 2 activator approved in the United States and the European Union for the treatment of patients with Friedreich ataxia aged ≥16 years, with a recommended dosage of 150 mg orally once daily on an empty stomach. The effect of the US Food and Drug Administration (FDA) high‐fat breakfast on the pharmacokinetic profile of omaveloxolone observed in study 408‐C‐1703 (NCT03664453) deviated from the usual linear correlation between fed/fasted maximum plasma concentration (Cmax) and area under the concentration–time curve (AUC) ratios reported for various oral drugs across 323 food effect studies. Here, physiologically based biopharmaceutics modeling (PBBM) was implemented to predict and explain the effect of the FDA high‐fat breakfast on a 150‐mg dose of omaveloxolone. The model was developed and validated based on dissolution and pharmacokinetic data available across dose‐ranging, food effect, and drug–drug interaction clinical studies. PBBM predictions support clinical observations of the unique effect of a high‐fat meal on omaveloxolone pharmacokinetic profile, in which the Cmax increased by 350% with only a 15% increase in the AUC. Key parameters influencing omaveloxolone pharmacokinetics in the fasted state based on a parameter sensitivity analysis included bile salt solubilization, CYP3A4 activity, drug substance particle size distribution, and permeability. Mechanistically, in vivo omaveloxolone absorption was solubility and dissolution rate limited. However, in the fed state, higher bile salt solubilization led to more rapid dissolution with predominant absorption in the upper gastrointestinal tract, resulting in increased susceptibility to first‐pass gut extraction; this accounts for the lack of correlation between Cmax and AUC for omaveloxolone.

Nusinersen clinical trials have limited data on adolescents and adults with 5q-associated spinal muscular atrophy (SMA). We conducted a systematic literature review (SLR) and meta-analysis to assess effectiveness of nusinersen in adolescents and adults with SMA in clinical practice. Our search included papers published 12/23/2016 through 07/01/2022 with ≥ 5 individuals ≥ 13 years of age and with ≥ 6 months’ data on ≥ 1 selected motor function outcomes [Hammersmith Functional Motor Scale–Expanded (HFMSE), Revised Upper Limb Module (RULM), and Six-Minute Walk Test (6MWT)]. For meta-analysis, effect sizes were pooled using random-effects models. To understand treatment effects by disease severity, subgroup meta-analysis by SMA type and ambulatory status was conducted. Fourteen publications including 539 patients followed up to 24 months met inclusion criteria for the SLR. Patients were age 13–72 years and most (99%) had SMA Type II or III. Modest improvement or stability in motor function was consistently observed at the group level. Significant mean increases from baseline were observed in HFMSE [2.3 points (95% CI 1.3–3.3)] with 32.1% (21.7–44.6) of patients demonstrating a clinically meaningful increase (≥ 3 points) at 18 months. Significant increases in RULM were consistently found, with a mean increase of 1.1 points (0.7–1.4) and 38.3% (30.3–47.1) showing a clinically meaningful improvement (≥ 2 points) at 14 months. Among ambulatory patients, there was a significant increase in mean 6MWT distance of 25.0 m (8.9–41.2) with 50.9% (33.4–68.2) demonstrating a clinically meaningful improvement (≥ 30 m) at 14 months. The increases in HFMSE were greater for less severely affected patients, whereas more severely affected patients showed greater improvement in RULM. Findings provide consolidated evidence that nusinersen is effective in improving or stabilizing motor function in many adolescents and adults with a broad spectrum of SMA.

Genome-wide association studies (GWAS) of human complex traits or diseases often implicate genetic loci that span hundreds or thousands of genetic variants, many of which have similar statistical significance. While statistical fine-mapping in individuals of European ancestry has made important discoveries, cross-population fine-mapping has the potential to improve power and resolution by capitalizing on the genomic diversity across ancestries. Here we present SuSiEx, an accurate and computationally efficient method for cross-population fine-mapping. SuSiEx integrates data from an arbitrary number of ancestries, explicitly models population-specific allele frequencies and linkage disequilibrium patterns, accounts for multiple causal variants in a genomic region and can be applied to GWAS summary statistics. We comprehensively assessed the performance of SuSiEx using simulations. We further showed that SuSiEx improves the fine-mapping of a range of quantitative traits available in both the UK Biobank and Taiwan Biobank, and improves the fine-mapping of schizophrenia-associated loci by integrating GWAS across East Asian and European ancestries.