Race, Genotype, and Azathioprine Discontinuation : A Cohort Study

SLCO1B1 Functional Variants, Bilirubin, Statin-Induced Myotoxicity, and Recent Sub-Saharan African Ancestry: A Precision Medicine Health Equity Study

Statin pharmacogenetic implementation guidelines are derived from evidence of primarily Eurocentrically biased study populations. Functional SLCO1B1 variants that are rare in these study populations have not been equitably investigated and are thus missing from guidelines. The objective of this precision medicine health equity study was to determine the clinical validity of understudied candidate functional SLCO1B1 variants common in people with 1,000 Genomes sub-Saharan African superpopulation (1KG-AFR-like) genetic similarity. We conducted our analyses using the real-world evidence of participants from three large, electronic health record-linked biobanks. We used bilirubin levels (as an endogenous substrate of organic anion transporting polypeptide [OATP1B1] function) and severe statin-induced myotoxicity phenotypes. Loss-of-function splice variant rs77271279 (P = 1.1 × 10-17) had the strongest association with elevated total bilirubin levels in Black participants (mean 84% AFR-like genetic similarity) followed by missense variant rs59502379 (P = 7.4 × 10-12) then missense variant rs4149056 (P = 6.0 × 10-5). In an exploratory subset of the Black study population who used statins (n = 77 severe statin-induced myotoxicity cases), rs59502379 (odds ratio [OR] = 2.85, 95% confidence interval [CI] 1.08-7.52), but not rs77271279 (OR = 1.75, 95% CI 0.62-4.73) was associated with myotoxicity. Sensitivity analyses in participants with >5% AFR-like genetic similarity corroborated these findings. For white participants, rs77271279 and rs59502379 were rare precluding subsequent analyses. Our findings highlight the clinical relevance for understudied SLCO1B1 variants on pharmacogenetic testing panels with a potential immediate impact on reducing the risk of severe statin-induced myotoxicity primarily in Black patients, a group historically excluded from genomic research. Future studies require larger statin user study populations with less heterogeneity by statin type.

PTPN2 and Leukopenia in Individuals With Normal TPMT and NUDT15 Metabolizer Status Taking Azathioprine

Leukopenia is a common dose-dependent side effect of azathioprine, often leading to drug discontinuation. Variants in TPMT and NUDT15 are associated with azathioprine-induced leukopenia but only explain 25% of cases. Thus, we aimed to identify novel genetic risk factors among TPMT and NUDT15 normal metabolizers through a genome-wide association study (GWAS). Using BioVU, Vanderbilt's electronic health record linked to genetic data, we assembled a discovery cohort of new users of azathioprine. The analysis was conducted in 1184 new users of azathioprine who had no history of prior thiopurine use or an organ transplant. A replication cohort of 521 patients was derived from All of Us, an NIH-funded project that links healthcare data and genetics. The GWAS was adjusted for sex, age, indication (inflammatory bowel disease, systemic lupus erythematosus, other autoimmune condition, or unknown), concurrent use of xanthine oxidase inhibitors (allopurinol or febuxostat) or immunosuppressants, prior TPMT or NUDT15 testing, and 10 principal components of ancestry. In BioVU, 65% of patients were female with a median age of 44 [IQR: 30, 57] and 125 patients developed leukopenia. In All of Us, 69% were female with a median age of 51 [36, 61], and 44 patients developed leukopenia. An intronic variant in PTPN2, rs11664064, reached genome-wide significance in BioVU (OR = 3.61; p = 1.96E-8) and replicated in All of Us (OR = 2.42, p = 0.039). Our finding suggests an association between rs11664064 in PTPN2 and azathioprine-induced leukopenia. PTPN2 plays a role in immune cell development and differentiation, providing a plausible mechanism for this association.

Characterization of the phenotypic consequences of the Duffy-null genotype

ABSTRACT

A wealth of research focused on African American populations has connected rs2814778-CC ("Duffy-null") to decreased neutrophil (neutropenia) and leukocyte counts (leukopenia). Although it has been proposed that this variant is benign, prior studies have shown that the misinterpretation of Duffy-null-associated neutropenia and leukopenia can lead to unnecessary bone marrow biopsies, inequities in cytotoxic and chemotherapeutic treatment courses, underenrollment in clinical trials, and other disparities. To investigate the phenotypic correlates of Duffy-null status, we conducted a phenome-wide association study across >1400 clinical conditions in All of Us, the Vanderbilt University Medical Center's Biobank, and the Million Veteran Program. This reveals that Duffy-null status is only reproducibly associated with changes in white blood cell count and not with any disease outcomes. Moreover, we find that Duffy-null-associated neutropenia is on average less severe than other neutropenia cases in All of Us. We also show that this genotype is present in considerable frequencies in All of Us populations that are genetically similar to African (68%) and Middle Eastern (14%) 1000 Genomes/Human Genome Diversity Project reference populations as well as those who identify with >1 race (12%), as Pacific Islander (7%), and as Hispanic (5%). Furthermore, we find that race is not an accurate predictor of Duffy-null status or associated benign neutropenia. Our research suggests that broad genetic screening of rs2814778 across all populations could provide a more robust and accurate understanding of white blood cell count and mitigate resulting health disparities.

Prurigo nodularis in 2025: Current and emerging treatments

Prurigo nodularis (PN) is a chronic inflammatory dermatologic condition that is often incredibly itchy and imposes a debilitating burden on patient quality of life. Patients have historically faced the hurdles of limited knowledge regarding the mechanisms underlying PN, physician awareness, and effective therapies. Many of the conventional treatments offer minimal benefit or are accompanied by adverse effects. Over the last several years, striking advancements in the understanding of the pathogenesis contributing to PN have allowed for the development of novel treatments. The first and only medication approved by the US Food and Drug Administration is dupilumab, a biological agent targeting interleukins 4 and 13, has revolutionized management for patients with moderate-to-severe PN. Several other drugs are on the horizon that have the potential to become widely available. This contribution aims to review the current and emerging therapies for PN and address the challenges that may hinder effective treatment.

Lupus and other autoimmune diseases: Epidemiology in the population of African ancestry and diagnostic and management challenges in Africa

Autoimmune diseases are prevalent among people of African ancestry living outside Africa. However, the burden of autoimmune diseases in Africa is not well understood. This article provides a global overview of the current burden of autoimmune diseases in individuals of African descent. It also discusses the major factors contributing to autoimmune diseases in this population group, as well as the challenges involved in diagnosing and managing autoimmune diseases in Africa.

Navigating Therapeutic Challenges of Pyoderma Gangrenosum in Felty's Syndrome: A Case Report and Literature Review

Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis characterized by painful skin ulcers. Treatment typically involves systemic corticosteroids, calcineurin inhibitors, or tumor necrosis factor-alpha inhibitors. Currently, treatment guidelines are not well established, making it important to consider alternative options in complicated cases. We report the case of a 52-year-old female with rheumatoid arthritis (RA) and a history of Felty's syndrome (FS) who developed PG and subsequently developed neutropenia due to azathioprine. The patient achieved remission with the use of dapsone and filgrastim. This treatment may be effective as an alternative for patients with RA and FS.

Using electronic health records for clinical pharmacology research: Challenges and considerations

Electronic health records (EHRs) contain a vast array of phenotypic data on large numbers of individuals, often collected over decades. Due to the wealth of information, EHR data have emerged as a powerful resource to make first discoveries and identify disparities in our healthcare system. While the number of EHR-based studies has exploded in recent years, most of these studies are directed at associations with disease rather than pharmacotherapeutic outcomes, such as drug response or adverse drug reactions. This is largely due to challenges specific to deriving drug-related phenotypes from the EHR. There is great potential for EHR-based discovery in clinical pharmacology research, and there is a critical need to address specific challenges related to accurate and reproducible derivation of drug-related phenotypes from the EHR. This review provides a detailed evaluation of challenges and considerations for deriving drug-related data from EHRs. We provide an examination of EHR-based computable phenotypes and discuss cutting-edge approaches to map medication information for clinical pharmacology research, including medication-based computable phenotypes and natural language processing. We also discuss additional considerations such as data structure, heterogeneity and missing data, rare phenotypes, and diversity within the EHR. By further understanding the complexities associated with conducting clinical pharmacology research using EHR-based data, investigators will be better equipped to design thoughtful studies with more reproducible results. Progress in utilizing EHRs for clinical pharmacology research should lead to significant advances in our ability to understand differential drug response and predict adverse drug reactions.

Prevalence of Duffy null and its impact on hydroxyurea in young children with sickle cell disease in the United States

Consistent with studies showing a high prevalence of the Duffy null phenotype among healthy Black Americans, this retrospective study found that Duffy null was present in >75% of a young and contemporary cohort of children with sickle cell disease (SCD) in the United States. Despite the potential for this phenotype to impact absolute neutrophil counts, hydroxyurea (HU) dosing, and outcomes, it was not associated with being prescribed a lower HU dose or having increased acute SCD visits early in the HU treatment course. Future studies are needed to confirm these findings in older children with SCD.

Clinical associations with a polygenic predisposition to benign lower white blood cell counts

Polygenic variation unrelated to disease contributes to interindividual variation in baseline white blood cell (WBC) counts, but its clinical significance is uncharacterized. We investigated the clinical consequences of a genetic predisposition toward lower WBC counts among 89,559 biobank participants from tertiary care centers using a polygenic score for WBC count (PGSWBC) comprising single nucleotide polymorphisms not associated with disease. A predisposition to lower WBC counts was associated with a decreased risk of identifying pathology on a bone marrow biopsy performed for a low WBC count (odds-ratio = 0.55 per standard deviation increase in PGSWBC [95%CI, 0.30-0.94], p = 0.04), an increased risk of leukopenia (a low WBC count) when treated with a chemotherapeutic (n = 1724, hazard ratio [HR] = 0.78 [0.69-0.88], p = 4.0 × 10-5) or immunosuppressant (n = 354, HR = 0.61 [0.38-0.99], p = 0.04). A predisposition to benign lower WBC counts was associated with an increased risk of discontinuing azathioprine treatment (n = 1,466, HR = 0.62 [0.44-0.87], p = 0.006). Collectively, these findings suggest that there are genetically predisposed individuals who are susceptible to escalations or alterations in clinical care that may be harmful or of little benefit.

Autoimmune inflammatory myopathy biomarkers

The autoimmune inflammatory myopathy disease spectrum, commonly known as myositis, is a group of systemic diseases that mainly affect the muscles, skin and lungs. Biomarker assessment helps in understanding disease mechanisms, allowing for the implementation of precise strategies in the classification, diagnosis, and management of these diseases. This review examines the pathogenic mechanisms and highlights current data on blood and tissue biomarkers of autoimmune inflammatory myopathies.

SLCO1B1 functional variants and statin-induced myopathy in people with recent genealogical ancestors from Africa: a population-based real-world study

Background

Clinical pharmacogenetic implementation guidelines for statin therapy are derived from evidence of primarily Eurocentric study populations. Functional SLCO1B1 variants that are rare in these study populations have not been investigated as a determinant of statin myotoxicity and are thus missing from guideline inclusion.

Objective

Determine the relationship between candidate functional SLCO1B1 variants and statin-induced myopathy in people with recent genealogical ancestors from Africa.

Design

Population-based pharmacogenetic study using real-world evidence from electronic health record-linked biobanks.

Setting

Various health care settings.

Participants

Self-identified white and Black statin users with genome-wide genotyping data available.

Measurements

Primarily, the odds of statin-induced myopathy + rhabdomyolysis. Secondarily, total bilirubin levels. Thirdly, cell-based functional assay results.

Results

Meta-analyses results demonstrated an increased risk of statin-induced myopathy + rhabdomyolysis with c.481+1G>T (odds ratio [OR] = 3.27, 95% confidence interval [CI] 1.43-7.46, P =.005) and c.1463G>C (OR = 2.45, 95% CI 1.04-5.78, P =.04) for Black participants. For White participants, c.521T>C was also significantly associated with increased risk of statin-induced myopathy + rhabdomyolysis (OR = 1.41, 95% CI 1.20-1.67, P =5.4x10 -5 ). This effect size for c.521T>C was similar in the Black participants, but did not meet the level of statistical significance (OR = 1.47, 95% CI 0.58-3.73, P =0.41). Supporting evidence using total bilirubin as an endogenous biomarker of SLCO1B1 function as well as from cell-based functional studies corroborated these findings.

Limitations

Data limited to severe statin myotoxicity events.

Conclusion

Our findings implicate Afrocentric SLCO1B1 variants on preemptive pharmacogenetic testing panels, which could have an instant impact on reducing the risk of statin-associated myotoxicity in historically excluded groups.

Primary Funding Source

National Institutes of Health, Office of the Director - All of Us (OD-AoURP).

Eliminating Algorithmic Racial Bias in Clinical Decision Support Algorithms: Use Cases from the Veterans Health Administration

The Veterans Health Administration uses equity- and evidence-based principles to examine, correct, and eliminate use of potentially biased clinical equations and predictive models. We discuss the processes, successes, challenges, and next steps in four examples. We detail elimination of the race modifier for estimated kidney function and discuss steps to achieve more equitable pulmonary function testing measurement. We detail the use of equity lenses in two predictive clinical modeling tools: Stratification Tool for Opioid Risk Mitigation (STORM) and Care Assessment Need (CAN) predictive models. We conclude with consideration of ways to advance racial health equity in clinical decision support algorithms.

Clinical consequences of a polygenic predisposition to benign lower white blood cell counts: Consequences of benign WBC count genetics

Polygenic variation unrelated to disease contributes to interindividual variation in baseline white blood cell (WBC) counts, but its clinical significance is undefined. We investigated the clinical consequences of a genetic predisposition toward lower WBC counts among 89,559 biobank participants from tertiary care centers using a polygenic score for WBC count (PGSWBC) comprising single nucleotide polymorphisms not associated with disease. A predisposition to lower WBC counts was associated with a decreased risk of identifying pathology on a bone marrow biopsy performed for a low WBC count (odds-ratio=0.55 per standard deviation increase in PGSWBC [95%CI, 0.30 - 0.94], p=0.04), an increased risk of leukopenia (a low WBC count) when treated with a chemotherapeutic (n=1,724, hazard ratio [HR]=0.78 [0.69 - 0.88], p=4.0×10-5) or immunosuppressant (n=354, HR=0.61 [0.38 - 0.99], p=0.04). A predisposition to benign lower WBC counts was associated with an increased risk of discontinuing azathioprine treatment (n=1,466, HR=0.62 [0.44 - 0.87], p=0.006). Collectively, these findings suggest that a WBC count polygenic score identifies individuals who are susceptible to escalations or alterations in clinical care that may be harmful or of little benefit.

Development of Duffy Null-Specific Absolute Neutrophil Count Reference Ranges

This study establishes a Duffy null phenotype–specific absolute neutrophil count reference range to optimize care and improve health equity.

Prospects for targeting ACKR1 in cancer and other diseases

The chemokine network is comprised of a family of signal proteins that encode messages for cells displaying chemokine G-protein coupled receptors (GPCRs). The diversity of effects on cellular functions, particularly directed migration of different cell types to sites of inflammation, is enabled by different combinations of chemokines activating signal transduction cascades on cells displaying a combination of receptors. These signals can contribute to autoimmune disease or be hijacked in cancer to stimulate cancer progression and metastatic migration. Thus far, three chemokine receptor-targeting drugs have been approved for clinical use: Maraviroc for HIV, Plerixafor for hematopoietic stem cell mobilization, and Mogalizumab for cutaneous T-cell lymphoma. Numerous compounds have been developed to inhibit specific chemokine GPCRs, but the complexity of the chemokine network has precluded more widespread clinical implementation, particularly as anti-neoplastic and anti-metastatic agents. Drugs that block a single signaling axis may be rendered ineffective or cause adverse reactions because each chemokine and receptor often have multiple context-specific functions. The chemokine network is tightly regulated at multiple levels, including by atypical chemokine receptors (ACKRs) that control chemokine gradients independently of G-proteins. ACKRs have numerous functions linked to chemokine immobilization, movement through and within cells, and recruitment of alternate effectors like β-arrestins. Atypical chemokine receptor 1 (ACKR1), previously known as the Duffy antigen receptor for chemokines (DARC), is a key regulator that binds chemokines involved in inflammatory responses and cancer proliferation, angiogenesis, and metastasis. Understanding more about ACKR1 in different diseases and populations may contribute to the development of therapeutic strategies targeting the chemokine network.

Leveraging our common African origins to understand human evolution and health

In the March 2023 issue of Cell, Fan et al.¹ report whole-genome sequencing across 12 indigenous African populations and analyze local adaptation and evolutionary history. Here, Wonkam and Adeyemo highlight their findings and how this contributes to African and global genomic research.

Association Between Genetically Predicted Expression of TPMT and Azathioprine Adverse Events

Polymorphisms thiopurine-S-methyltransferase (TPMT) and nudix hydrolase 15 (NUDT15) can increase the risk of azathioprine myelotoxicity, but little is known about other genetic factors that increase risk for azathioprine-associated side effects. PrediXcan is a gene-based association method that estimates the expression of individuals' genes and examines their correlation to specified phenotypes. As proof of concept for using PrediXcan as a tool to define the association between genetic factors and azathioprine side effects, we aimed to determine whether the genetically predicted expression of TPMT or NUDT15 was associated with leukopenia or other known side effects. In a retrospective cohort of 1364 new users of azathioprine with EHR-reported White race, we used PrediXcan to impute expression in liver tissue, tested its association with pre-specified phecodes representing known side effects (e.g., skin cancer), and completed chart review to confirm cases. Among confirmed cases, patients in the lowest tertile (i.e., lowest predicted) of TPMT expression had significantly higher odds of developing leukopenia (OR=3.30, 95%CI: 1.07-10.20, p=0.04) versus those in the highest tertile; no other side effects were significant. The results suggest that this methodology could be deployed on a larger scale to uncover associations between genetic factors and drug side effects for more personalized care.

Ancestry, ACKR1 and leucopenia in patients with systemic lupus erythematosus

OBJECTIVE

SLE is more prevalent in populations of African (AA) than European ancestry (EA) and leucopenia is common. A homozygous variant in ACKR1 (rs2814778-CC) is associated with lower white cell counts; the variant is common in AA but not EA populations. We hypothesised that in SLE: (1) leucopenia is more frequent in patients of AA than EA, and (2) the ACKR1-CC genotype accounts for the higher frequency of leucopenia in AA patients.

METHODS

We performed a retrospective cohort study in patients with SLE at a tertiary care system. Ancestry was defined by genetic principal components. We compared the rate of leucopenia, thrombocytopenia and anaemia between (a) EA and AA patients, and (b) ACKR1-CT/TT and CC genotype in AA patients.

RESULTS

The cohort included 574 patients of EA and 190 of AA; ACKR1-CC genotype was common in AA (70%) but not EA (0%) patients. Rates of leucopenia for ancestry and genotype were AA 60.0% vs EA 36.8 % (p=1.9E-08); CC 67.7% vs CT/TT 42.1% (p=9.8E-04). The rate of leucopenia did not differ by ancestry comparing EA patients versus AA with CT/TT genotype (p=0.59). Thrombocytopenia (22.2% vs 13.2%, p=0.004) and anaemia (88.4% vs 66.2%, p=3.7E-09) were more frequent in AA patients but were not associated with ACKR1 genotype (p=0.82 and p=0.84, respectively).

CONCLUSIONS

SLE of AA had higher rates of anaemia, leucopenia, and thrombocytopenia than those of EA; only the difference in leucopenia was explained by ACKR1-CC genotype. This genotype could affect clinical practice.

Absolute neutrophil count by Duffy status among healthy Black and African American adults

Many people of African ancestry have lower absolute neutrophil counts (ANCs) without increased risk for infection. This is associated with the Duffy-null phenotype (nonexpression of the Duffy antigen on red blood cells), which is commonly found in those of African descent. Currently, there are no studies that compare the ANC of individuals with Duffy-null phenotype to those with Duffy non-null phenotypes within a self-identified Black population. The aim of this study was to assess the impact of Duffy status on ANCs based on complete blood counts with differential and Duffy testing in a healthy population of self-identified Black individuals at a single primary care center. This study found that 66.7% (80 of 120) of Black individuals have the Duffy-null phenotype and that there is a significant difference in ANCs between Duffy-null and Duffy non-null individuals (median, 2820 cells per μL vs 5005 cells per μL; P < .001). Additionally, 19 of 80 (23.8%) Duffy-null individuals had an ANC of <2000 cells per μL compared with no (0) Duffy non-null individuals. The Duffy-null phenotype is clinically insignificant; however, inappropriate reference ranges can propagate systemic racism. Therefore, we advocate for the development of Duffy-null-specific ANC reference ranges as well as replacing the term benign ethnic neutropenia with Duffy-nullassociated neutrophil count.