HER2-targeted antibody-drug conjugates for breast cancer: ancestry and dose adjustment for thrombocytopenia

BACKGROUND

Thrombocytopenia is a common adverse event on HER2-targeted therapies, fam-trastuzumab deruxtecan (T-DXd) and ado-trastuzumab emtansine (T-DM1). A reported association of Asian ancestry with this event merits investigation to rule out potential confounding.

METHODS

Subjects in this retrospective cohort were female patients with HER2 positive breast cancer, of Asian or non-Hispanic White ancestry, who initiated T-DM1 or T-DXd from January 2017 through October 2021. Follow-up closed in January 2022. Primary endpoint was dose adjustment for thrombocytopenia. Competing endpoints were discontinuation of drug for other toxicity, disease progression, or for completion of prescribed cycles. The association between Asian ancestry and thrombocytopenia-related dose adjustment was tested at p < 0.01 in a proportional hazards model for the sub-distributions of 4 (primary and competing) endpoints. Covariates examined as potential confounders were age, metastatic disease, specific HER2-targeted drug, and prior drug switching for toxicity.

RESULTS

Among 181 subjects, 48 reported Asian ancestry. Incidence of dose adjustment for thrombocytopenia was higher in patients with Asian ancestry and among patients switched to T-DXd after experiencing thrombocytopenia on T-DM1. Independent of specific drug and prior drug switching, Asian ancestry was associated with dose adjustment for thrombocytopenia (hazards ratio 2.95, 95% confidence interval 1.41-6.18) but not with competing endpoints. Among participants of Asian ancestry, the ancestral origin was usually China or the Philippines (where Chinese ancestry is common).

CONCLUSIONS

The association between Asian ancestry and thrombocytopenia on HER2-targeted therapy is independent of age, metastatic disease, drug, and history of similar toxicity. This association may have a genetic basis linked to Chinese ancestry.

The frequency of rs2231142 in ABCG2 among Asian subgroups: implications for personalized rosuvastatin dosing

Statins are widely used medications for the primary and secondary prevention of cardiovascular diseases. Statin-induced musculoskeletal symptoms are the primary adverse drug events contributing to poor adherence to lipid-lowering therapy. Rosuvastatin is characterized by interindividual differences in systemic exposure among different patient population subgroups. The missense variant Q141K within ABCG2, highly prevalent in some Asian subgroups, results in decreased transporter efflux function and increased exposure to rosuvastatin. We aim to highlight the implications of ABCG2 genotype in prescribing rosuvastatin and the ramifications of interpopulation differences in Q141K frequencies in the starting dose of rosuvastatin in major Asian subgroups, using the most recent genetic-based guidelines. The high frequency of Q141K in Filipinos could warrant a lower starting rosuvastatin dose versus non-Filipinos. The Q141K genotype frequencies in Asian subgroups suggest significant interpopulation differences, reinforcing the need to move beyond race-based to genotype-based rosuvastatin dosing.

The Epidemiology and Phenotypes of Ocular Manifestations in Childhood and Juvenile Myasthenia Gravis: A Review

Myasthenia gravis (MG) appears to have a similar incidence among adult populations worldwide. However, epidemiological and phenotypic differences have been noted among children and juveniles with MG. We reviewed the literature on childhood- and juvenile-onset MG among different populations, with the focus on ocular involvement, antibody profiles, the genetic susceptibility to juvenile MG phenotypes, the use of immune treatments, and the reported responses of extraocular muscles to therapies. Although epidemiological studies used different methodologies, reports from Asia, compared to Europe, showed more than two-fold higher proportions of prepubertal onset (before 12 years) vs. postpubertal-onset juveniles with MG. Compared to European children, ocular MG was 4-fold more frequent among Asian children, and 2–3-fold more frequent among children with African ancestry both in prepubertal and postpubertal ages at onset. These results suggest genetic influences. In Asia, HLA-B^*46 and DRB1^*09 appeared overrepresented in children with ocular MG. In Europe, children with MG had a significantly higher rate of transforming from ocular to generalized disease and with an overrepresentation of HLADRB1^*04. Although treatment regimens vary widely and the responses to immune therapies of the ocular muscles involved in MG were generally poorly described, there were indications that earlier use of steroid therapy may have better outcomes. Reports of treatment-resistant ophthalmoplegia may be more frequent in African and Asian juvenile MG cohorts compared to Europeans. Genetic and muscle gene expression studies point to dysregulated muscle atrophy signaling and mitochondrial metabolism pathways as pathogenetic mechanisms underpinning treatment-resistant ophthalmoplegia in susceptible individuals. In conclusion, phenotypic differences in juveniles with ocular manifestations of MG were evident in different populations suggesting pathogenetic influences. Treatment responses in MG-associated ocular disease should attract more careful descriptive reports. In MG, extraocular muscles may be vulnerable to critical periods of poor force generation and certain individuals may be particularly susceptible to developing treatment-resistant ophthalmoplegia. The development of prognostic biomarkers to identify these susceptible individuals is an unmet need.

High-sensitivity Troponin I Predicts Galectin-3 in Chronic Kidney Disease Patients

PURPOSE

Plasma galectin-3 (pG3) regulates inflammation. B-type natriuretic peptide (BNP), high-sensitivity Troponin I (hsTnI), and pG3 concentrations are elevated in chronic kidney disease (CKD) patients. The associations of pG3 with hsTnI/BNP are unclear. We explored the relationship of hsTnI and BNP with pG3 in Asian CKD patients and healthy controls.

METHODS

We retrieved prospectively collected frozen plasma samples from 163 stable CKD patients and 105 healthy controls. BNP, hsTnI and pG3 were assayed. pG3 was assessed for associations with age, gender, ethnicity, blood pressures; height, weight, body mass index (BMI), previously diagnosed CKD, diabetes, hypertension, coronary artery disease, estimated glomerular filtration rate (eGFR); C-reactive protein, beta-trace protein, 24 h urine protein, serum albumin, uric acid and cystatin C. We created two models predicting pG3 using multiple linear regression. Akaike Information Criterion (AIC) was used for comparison. Significance was taken at P < 0.05.

RESULTS

CKD versus healthy participants: mean BMI (28.2 vs. 24.9 kg/m²), median serum creatinine (159 vs. 69 µmol/L; 1.8 vs. 0.78 mg/dL), median eGFR (49 vs. 104 mL/min/1.73m²), median pG3 (29.4 vs. 15.4 ng/mL), median BNP (136 vs. 23 pg/mL), and median hsTnI (12.5 vs. 2.6 pg/mL). By univariate analysis, all variables are associated with pG3 except weight, gender and diagnosis of cerebrovascular or peripheral vascular diseases. A parsimonious model selected for hsTnI, BMI, serum albumin, cystatin C and eGFR (AIC = 77.6).

CONCLUSION

BNP and hsTnI are associated with pG3 in Asian CKD patients. hsTnI is a better predictor of pG3.

Genome-wide association studies identify susceptibility loci for epithelial ovarian cancer in east Asian women

OBJECTIVE

Genome-wide association studies (GWASs) for epithelial ovarian cancer (EOC) have focused largely on populations of European ancestry. We aimed to identify common germline variants associated with EOC risk in Asian women.

METHODS

Genotyping was performed as part of the OncoArray project. Samples with >60% Asian ancestry were included in the analysis. Genotyping was performed on 533,631 SNPs in 3238 Asian subjects diagnosed with invasive or borderline EOC and 4083 unaffected controls. After imputation, genotypes were available for 11,595,112 SNPs to identify associations.

RESULTS

At chromosome 6p25.2, SNP rs7748275 was associated with risk of serous EOC (odds ratio [OR] = 1.34, P = 8.7 × 10-9) and high-grade serous EOC (HGSOC) (OR = 1.34, P = 4.3 × 10-9). SNP rs6902488 at 6p25.2 (r2 = 0.97 with rs7748275) lies in an active enhancer and is predicted to impact binding of STAT3, P300 and ELF1. We identified additional risk loci with low Bayesian false discovery probability (BFDP) scores, indicating they are likely to be true risk associations (BFDP <10%). At chromosome 20q11.22, rs74272064 was associated with HGSOC risk (OR = 1.27, P = 9.0 × 10-8). Overall EOC risk was associated with rs10260419 at chromosome 7p21.3 (OR = 1.33, P = 1.2 × 10-7) and rs74917072 at chromosome 2q37.3 (OR = 1.25, P = 4.7 × 10-7). At 2q37.3, expression quantitative trait locus analysis in 404 HGSOC tissues identified ESPNL as a putative candidate susceptibility gene (P = 1.2 × 10-7).

CONCLUSION

While some risk loci were shared between East Asian and European populations, others were population-specific, indicating that the landscape of EOC risk in Asian women has both shared and unique features compared to women of European ancestry.

Ancestral characterization of 1018 cancer cell lines highlights disparities and reveals gene expression and mutational differences

Background

Although cell lines are an essential resource for studying cancer biology, many are of unknown ancestral origin, and their use may not be optimal for evaluating the biology of all patient populations.

Methods

An admixture analysis was performed using genome‐wide chip data from the Catalogue of Somatic Mutations in Cancer (COSMIC) Cell Lines Project to calculate genetic ancestry estimates for 1018 cancer cell lines. After stratifying the analyses by tissue and histology types, linear models were used to evaluate the influence of ancestry on gene expression and somatic mutation frequency.

Results

For the 701 cell lines with unreported ancestry, 215 were of East Asian origin, 30 were of African or African American origin, and 453 were of European origin. Notable imbalances were observed in ancestral representation across tissue type, with the majority of analyzed tissue types having few cell lines of African American ancestral origin, and with Hispanic and South Asian ancestry being almost entirely absent across all cell lines. In evaluating gene expression across these cell lines, expression levels of the genes neurobeachin line 1 (NBEAL1), solute carrier family 6 member 19 (SLC6A19), HEAT repeat containing 6 (HEATR6), and epithelial cell transforming 2 like (ECT2L) were associated with ancestry. Significant differences were also observed in the proportions of somatic mutation types across cell lines with varying ancestral proportions.

Conclusions

By estimating genetic ancestry for 1018 cancer cell lines, the authors have produced a resource that cancer researchers can use to ensure that their cell lines are ancestrally representative of the populations they intend to affect. Furthermore, the novel ancestry‐specific signal identified underscores the importance of ancestral awareness when studying cancer.

Preclinical cancer cell line research is often conducted without an awareness of ancestral background, which results in incongruities between the genetic backgrounds of used cell lines and the patient populations they are intended to represent. By calculating genetic ancestry for 1018 common cancer cell lines and identifying ancestry‐specific expression and somatic mutation patterns, the importance of ancestral awareness is emphasized, and a resource is provided that can be used by cancer researchers to ensure that their cell lines are ancestrally representative of the populations they aim to impact.

High burden of birthweight-lowering genetic variants in Africans and Asians

BACKGROUND

Birthweight is an important predictor of infant morbidity and mortality, and is associated with cardiovascular diseases, obesity, and diabetes in childhood and adulthood. Birthweight and fetal growth show regional and population variations even under similar maternal conditions, and a large proportion of these differences are not explained by environmental factors. Whether and to what extent population genetic variations at key birthweight-associated loci account for the residual birthweight disparities not explained by environmental determinants is unknown. We hypothesized that the cumulative burden of genetic variants with a birthweight-lowering effect (GRB) is different among ancestrally diverse populations.

METHODS

Genotype data were extracted from phase 3 of the 1000 Genomes Project for 2504 participants from 26 global populations grouped into five super-populations. GRB was calculated in offspring as the weighted sum of the number of birthweight-lowering genetic variants of 59 autosomal single-nucleotide polymorphisms associated with birthweight, and comparisons were made between Europeans and non-Europeans.

RESULTS

GRB was significantly higher in Africans (mean difference 3.15; 95% confidence interval 2.64, 3.66), admixed Americans (3.02; 2.34, 3.70), East Asians (2.85; 2.29, 3.41), and South Asians (1.07; 0.49, 1.65) compared to Europeans. Birthweight-lowering genetic variants in Africans and East Asians were enriched for rare and frequency-fixed alleles (P < 0.001). African and Asian populations had the greatest deviation from the expectation of the common disease-common variant hyothesis. Compared to Europeans, the GRB of ancestral alleles was significantly higher and that of derived alleles was significantly lower in non-Europeans (P < 0.001).

CONCLUSIONS

The burden of birthweight-lowering genetic variants is higher in Africans and East Asians. This finding is consistent with the high incidence of low birthweight in the two populations. The genetic variants we studied may not be causal and the extent to which they tag the causal variants in non-Europeans is unknown; however, our findings highlight that genetic variations contribute to population differences in birthweight.