Potential and challenges of clinical high-dimensional flow cytometry: A call to action.

Clinical biomarker strategies increasingly integrate translational research to gain new insights into disease mechanisms or to define better biomarkers in clinical trials. High-dimensional flow cytometry (HDFCM) holds the promise to enhance the exploratory potential beyond traditional, targeted biomarker strategies. However, the increased complexity of HDFCM poses several challenges, which need to be addressed in order to fully leverage its potential and to align with current regulatory requirements in clinical flow cytometry. These challenges include among others extended timelines for assay development and validation, the necessity for extensive knowledge in HDFCM, and sophisticated data analysis strategies. However, no guidelines exist on how to manage such challenges in adopting clinical HDFCM. Our CYTO 2024 workshop "Potential and challenges of clinical high-dimensional flow cytometry" aimed to find consensus across the pharmaceutical industry and broader scientific community on the overall benefits and most urgent challenges of HDFCM in clinical trials. Here, we summarize the insights we gained from our workshop. While this report does not provide a blueprint, it is a first step in defining and summarizing the most pressing challenges in implementing HDFCM in clinical trials. Furthermore, we compile current efforts with the goal to overcome some of these challenges. As such we bring the scientific community and health authorities together to build solutions, which will accelerate and simplify the full adoption of HDFCM in clinical trials.

Autistic and autism community perspectives on infant and family support in the first two years of life: Findings from a community consultation survey.

LAY ABSTRACT: Most support programmes for Autistic children are available only after they are diagnosed. Research suggests that parenting supports may be helpful for parents and their infants, when provided in the first 2 years of life - before a formal diagnosis is given, but when information suggests an infant is more likely to be Autistic. However, we do not know how acceptable these types of supports might be to the Autistic and autism communities. We asked 238 Autistic and non-autistic people - some of whom were parents, and some of whom were professionals working in research, health and education - about their perspectives on very-early supports. People generally agreed that it could be acceptable to work with parents to help them understand and support their child's specific needs and unique ways of communicating. People suggested a variety of support strategies could be acceptable, including parent education, changing the environment to meet an infant's needs, and creating opportunities for infants' to make choices and exercise control. People preferred respectful and accurate language - including the term 'support' (rather than 'intervention') and 'early-in-life' (rather than 'at-risk' of autism, or 'pre-emptive' when describing developmental stage). Continuing to work with community members will help to make sure autism support programmes are relevant and helpful.

Predictors of Change in Wellbeing and Mental Health of Parents of Autistic Pre-Schoolers.

Parenting is a rewarding experience but is not without its challenges. Parents of Autistic children face additional challenges, and as a result can experience lower levels of wellbeing and more mental health problems (i.e., depression, anxiety, stress). Previous studies have identified concurrent correlates of wellbeing and mental health. However, few have investigated predictors of subsequent wellbeing and mental health, or of change over time, among parents of pre-school aged autistic children. We examined child-, parent-, and family/sociodemographic factors associated with change in parents' mental health and wellbeing across three timepoints (spanning approximately one year) among 53 parents of Autistic pre-schoolers (M = 35.48, SD = 6.36 months. At each timepoint, parents reported lower wellbeing and greater mental health difficulties compared to normative data. There was no significant group-level change over time in parent outcomes. However, individual variability in short-term (~ 5 months) wellbeing and mental health change was predicted by a combination of child- and parent-related factors, while variability in medium-term (~ 10 months) change was predicted by parent factors alone. Parents' description of their child and their relationship predicted change in both wellbeing and mental health. Furthermore, participating in a parent-mediated intervention (available to a subgroup) was a significant predictor of change in wellbeing. Our findings highlight potentially modifiable factors (e.g., learning healthier coping strategies) that may positively impact both short- and medium-term change in parental outcomes.

Recommendations for using artificial intelligence in clinical flow cytometry.

Flow cytometry is a key clinical tool in the diagnosis of many hematologic malignancies and traditionally requires close inspection of digital data by hematopathologists with expert domain knowledge. Advances in artificial intelligence (AI) are transferable to flow cytometry and have the potential to improve efficiency and prioritization of cases, reduce errors, and highlight fundamental, previously unrecognized associations with underlying biological processes. As a multidisciplinary group of stakeholders, we review a range of critical considerations for appropriately applying AI to clinical flow cytometry, including use case identification, low and high risk use cases, validation, revalidation, computational considerations, and the present regulatory frameworks surrounding AI in clinical medicine. In particular, we provide practical guidance for the development, implementation, and suggestions for potential regulation of AI-based methods in the clinical flow cytometry laboratory. We expect these recommendations to be a helpful initial framework of reference, which will also require additional updates as the field matures.

Prospective Association of Parenting Stress with Later Child Behavior Problems in Early Childhood Autism.

PURPOSE: Autistic children are reported to display higher levels of externalizing and internalizing behaviors than neurotypical children, and their parents report more stress than parents of neurotypical children. It is unclear whether child behavior difficulties contribute to increased parenting stress, whether parenting stress contributes to child behavior difficulties, or whether the relationship may be bidirectional. METHODS: We investigated prospective bidirectional associations between parenting stress and child externalizing and internalizing behaviors when autistic children were aged on average 3.5, 4.5, and 5.5 years. Data collected at these three timepoints were examined across two panels: Time 1 to Time 2 (n = 38 parent-child dyads) and Time 2 to Time 3 (n = 27 dyads). RESULTS: Across Time 1 to Time 2, early parenting stress was significantly associated with later child externalizing behavior, and cross-lagged panel analysis supported a uni- rather than a bidirectional association between these factors. There was some evidence of a bidirectional association between parenting stress and child internalizing behavior, though this was non-significant when the strong stability of child internalizing behavior was statistically controlled. In contrast, across Time 2 to Time 3, there were no significant prospective associations found between variables, highlighting the importance of considering the impact of parenting stress early in the course of childhood autism. CONCLUSION: Our results add to research indicating that support targeting parent characteristics, especially parenting stress, could ameliorate subsequent outcomes for both parents and children.

Endophenotyping social cognition in the broader autism phenotype.

Relatives of individuals with autism spectrum disorder (ASD) may display milder social traits of the broader autism phenotype (BAP) providing potential endophenotypic markers of genetic risk for ASD. We performed a case-control comparison to quantify social cognition and pragmatic language difficulties in the BAP (n = 25 cases; n = 33 controls) using the Faux Pas test (FPT) and the Goldman-Eisler Cartoon task. Using deep phenotyping we then examined patterns of inheritance of social cognition in two large multiplex families and the spectrum of performance in 32 additional families (159 members; n = 51 ASD, n = 87 BAP, n = 21 unaffected). BAP individuals showed significantly poorer FPT performance and reduced verbal fluency with the absence of a compression effect in social discourse compared to controls. In multiplex families, we observed reduced FPT performance in 89% of autistic family members, 63% of BAP relatives and 50% of unaffected relatives. Across all affected families, there was a graded spectrum of difficulties, with ASD individuals showing the most severe FPT difficulties, followed by the BAP and unaffected relatives compared to community controls. We conclude that relatives of probands show an inherited pattern of graded difficulties in social cognition with atypical faux pas detection in social discourse providing a novel candidate endophenotype for ASD.

Flow Cytometry Method Validation Protocols.

Analytical method validation provides a means to ensure that data are credible and reproducible. This article will provide a brief introduction to analytical method validation as applied to cellular analysis by flow cytometry, along with practical procedures for four different types of validation. The first, Basic Protocol 1 (the limited validation protocol), is recommended for research and non-regulated laboratories. Next, Basic Protocol 2) presents a reasonable, fit-for-purpose validation approach appropriate for biopharma and research settings. Basic Protocol 3 addresses the type of validation performed in clinical laboratories for moderate-risk tests developed in house. Finally, Basic Protocol 4 describes the process that should be applied whenever a method is being transferred from one facility to another. All four validation plans follow the fit-for-purpose validation approach, in which the validation parameters are selected based on the intended use of the assay. These validation protocols represent the minimal requirement and may not be applicable for every intended use such as high-risk clinical assays or data to be used as a primary endpoint in a clinical trial. The recommendations presented here are consistent with the white papers published by the American Association of Pharmaceutical Scientists and the International Clinical Cytometry Society, as well as with Clinical Laboratory Standards Institute Guideline H62: Validation of Assays Performed by Flow Cytometry (CLSI, 2021). © 2023 Wiley Periodicals LLC. Basic Protocol 1: Limited validation Basic Protocol 2: Fit-for-purpose validation for biopharma and research settings Basic Protocol 3: Validation for moderate clinical risk laboratory developed tests Basic Protocol 4: Transfer validation.

The first six months of life: A systematic review of early markers associated with later autism.

There is now good evidence that behavioural signs of autism spectrum conditions (autism) emerge over the first two years of life. Identifying clear developmental differences early in life may facilitate earlier identification and intervention that can promote longer-term quality of life. Here we present a systematic review of studies investigating behavioural markers of later autism diagnosis or symptomology taken at 0-6 months. The following databases were searched for articles published between 01/01/2000 and 15/03/2022: Embase, Medline, Scopus, PubMed, PsycINFO, CINAHL, Web of Science and Proquest. Twenty-five studies met inclusion criteria: assessment of behaviour at 0-6 months and later assessment of autism symptomology or diagnosis. Studies examined behaviours of attention, early social and communication behaviours, and motor behaviours, as well as composite measures. Findings indicated some evidence of measures of general attention, attention to social stimuli, and motor behaviours associated with later autism diagnosis or symptomology. Findings were inconsistent regarding social and communication behaviours, with a lack of repeated or validated measures limiting drawing firm conclusions. We discuss implications of the findings and suggest recommendations for future research.

Development of a novel, highly sensitive assay for quantification of minimal residual B cells in autoimmune disease and comparison to traditional methods across B-cell-depleting agents.

Targeted B-cell depletion is a useful therapy for many diseases, including autoimmune disorders and certain cancers. We developed a sensitive blood B-cell depletion assay, MRB 1.1, compared its performance with the T-cell/B-cell/NK-cell (TBNK) assay, and assessed B-cell depletion with different therapies. The empirically defined lower limit of quantification (LLOQ) for CD19+ cells in the TBNK assay was 10 cells/µL, and 0.441 cells/µL for the MRB 1.1 assay. The TBNK LLOQ was used to compare differences between B-cell depletion in similar lupus nephritis patient populations who received rituximab (LUNAR), ocrelizumab (BELONG), or obinutuzumab (NOBILITY). After 4 weeks, 10% of patients treated with rituximab retained detectable B cells vs 1.8% with ocrelizumab and 1.7% for obinutuzumab; at 24 weeks 93% of patients who received obinutuzumab remained below LLOQ vs 63% for rituximab. More-sensitive measurements of B cells may reveal differences in potency among anti-CD20 agents, which may associate with clinical outcomes.

Unexpected diagnosis of myotonic dystrophy type 2 repeat expansion by genome sequencing.

Several neurological disorders, such as myotonic dystrophy are caused by expansions of short tandem repeats (STRs) which can be difficult to detect by molecular tools. Methodological advances have made repeat expansion (RE) detection with whole genome sequencing (WGS) feasible. We recruited a multi-generational family (family A) ascertained for genetic studies of autism spectrum disorder. WGS was performed on seven children from four nuclear families from family A and analyzed for REs of STRs known to cause neurological disorders. We detected an expansion of a heterozygous intronic CCTG STR in CNBP in two siblings. This STR causes myotonic dystrophy type 2 (DM2). The expansion did not segregate with the ASD phenotype. Repeat-primed PCR showed that the DM2 CCTG motif was expanded above the pathogenic threshold in both children and their mother. On subsequent examination, the mother had mild features of DM2. We show that screening of STRs in WGS datasets has diagnostic utility, both in the clinical and research domain, with potential management and genetic counseling implications.

Parental Imitations and Expansions of Child Language Predict Later Language Outcomes of Autistic Preschoolers.

Both the amount and responsiveness of adult language input contribute to the language development of autistic and non-autistic children. From parent-child interaction footage, we measured the amount of adult language input, overall parent responsiveness, and six discrete parent responsive behaviours (imitations, expansions, open-ended questions, yes/no questions, comments and acknowledgements) to explore which types of responsiveness predicted autistic preschoolers' language five months later, after controlling for adult language input. We found expansions and particularly imitations to be more important for later language than overall responsiveness. This study emphasises the need to capture what exactly about parent language input influences child language acquisition, and adds to the evidence that imitating and expanding early language might be particularly beneficial for autistic preschoolers.

Venetoclax and idasanutlin in relapsed/refractory AML: a nonrandomized, open-label phase 1b trial.

This phase 1b trial (NCT02670044) evaluated venetoclax-idasanutlin in patients with relapsed/refractory (R/R) acute myeloid leukemia (AML) ineligible for cytotoxic chemotherapy. Two-dimensional dose escalation (DE, n = 50) was performed for venetoclax daily with idasanutlin on days 1 to 5 in 28-day cycles, followed by dosing schedule optimization (n = 6) to evaluate reduced venetoclax schedules (21-/14-day dosing). Common adverse events (occurring in ≥40% of patients) included diarrhea (87.3% of patients), nausea (74.5%), vomiting (52.7%), hypokalemia (50.9%), and febrile neutropenia (45.5%). During DE, across all doses, composite complete remission (CRc; CR + CR with incomplete blood count recovery + CR with incomplete platelet count recovery) rate was 26.0% and morphologic leukemia-free state (MLFS) rate was 12%. For anticipated recommended phase 2 doses (venetoclax 600 mg + idasanutlin 150 mg; venetoclax 600 mg + idasanutlin 200 mg), the combined CRc rate was 34.3% and the MLFS rate was 14.3%. Pretreatment IDH1/2 and RUNX1 mutations were associated with higher CRc rates (50.0% and 45.0%, respectively). CRc rate in patients with TP53 mutations was 20.0%, with responses noted among those with co-occurring IDH and RUNX1 mutations. In 12 out of 36 evaluable patients, 25 emergent TP53 mutations were observed; 22 were present at baseline with low TP53 variant allele frequency (median 0.0095% [range, 0.0006-0.4]). Venetoclax-idasanutlin showed manageable safety and encouraging efficacy in unfit patients with R/R AML. IDH1/2 and RUNX1 mutations were associated with venetoclax-idasanutlin sensitivity, even in some patients with co-occurring TP53 mutations; most emergent TP53 clones were preexisting. Our findings will aid ongoing/future trials of BCL-2/MDM2 inhibitor combinations. This trial was registered at www.clinicaltrials.gov as #NCT02670044.

A phase 1b study of atezolizumab in combination with guadecitabine for the treatment of acute myeloid leukemia.

This phase 1 b study evaluated the safety, efficacy, and pharmacokinetics of atezolizumab in combination with guadecitabine in patients with relapsed/refractory (R/R) or first-line acute myeloid leukemia (AML). Patients received atezolizumab 840 mg (days [D] 8 and 22) and guadecitabine 60 mg/m2 (D1 and D5) over 28-day cycles. Sixteen patients (median age 73.0 years) enrolled (R/R cohort, n = 11; first-line cohort, n = 5). All patients reported at least 1 AE; 15 patients (93.8%) reported grade ≥ 3 AEs, and 15 patients (93.8%) reported SAEs. Fourteen of the 16 patients (87.5%) died during the trial period due to disease progression (8/14) or AEs (6/14), hence the study was terminated early. One patient (from the R/R AML cohort) achieved a response (CR with incomplete platelet recovery) with a DOR of 27.8 months at study termination. Atezolizumab plus guadecitabine had limited clinical activity in AML and an overall unfavorable benefit-risk profile at the investigated dose levels.

Atezolizumab alone or in combination did not demonstrate a favorable risk-benefit profile in myelodysplastic syndrome.

We present primary results from the phase 1b GO29754 study evaluating the safety and tolerability of atezolizumab, a programmed death-ligand 1 inhibitor, alone and in combination with azacitidine, a hypomethylating agent (HMA), in patients with relapsed/refractory (R/R) or HMA-naïve myelodysplastic syndrome (MDS). Patients with R/R MDS received atezolizumab for 12 months (cohort A) or atezolizumab plus azacitidine for 6 cycles followed by atezolizumab as maintenance for 8 cycles (cohort B). Patients with HMA-naïve MDS received atezolizumab plus azacitidine until loss of clinical benefit (cohort C). Safety, activity, and exploratory end points were investigated. Forty-six patients were enrolled and received treatment (cohort A, n = 11; cohort B, n = 14; cohort C, n = 21). All patients experienced ≥1 adverse event (AE) on study, and all patients discontinued atezolizumab. In cohort A, 7 patients (63.6%) died, and no patients responded. In cohort B, 8 patients (57.1%) discontinued azacitidine, 11 (78.6%) died, and 2 (14.3%) responded. In cohort C, all 21 patients discontinued azacitidine, 13 died (61.9%), and 13 (61.9%) responded. The study was terminated by the sponsor before completion of recruitment because of the unexpected high early death rate in cohort C (6 [46.2%] of 13 deaths were due to AEs and occurred within the first 4 treatment cycles.). The high death rate and poor efficacy observed in this study do not support a favorable risk-benefit profile for atezolizumab as a single agent or in combination with azacitidine in R/R or HMA-naïve MDS. This trial was registered at www.clinicaltrials.gov as #NCT02508870.

A family study implicates GBE1 in the etiology of autism spectrum disorder.

Autism spectrum disorders (ASD) are neurodevelopmental disorders with an estimated heritability of >60%. Family-based genetic studies of ASD have generally focused on multiple small kindreds, searching for de novo variants of major effect. We hypothesized that molecular genetic analysis of large multiplex families would enable the identification of variants of milder effects. We studied a large multigenerational family of European ancestry with multiple family members affected with ASD or the broader autism phenotype (BAP). We identified a rare heterozygous variant in the gene encoding 1,4-ɑ-glucan branching enzyme 1 (GBE1) that was present in seven of seven individuals with ASD, nine of ten individuals with the BAP, and none of four tested unaffected individuals. We genotyped a community-acquired cohort of 389 individuals with ASD and identified three additional probands. Cascade analysis demonstrated that the variant was present in 11 of 13 individuals with familial ASD/BAP and neither of the two tested unaffected individuals in these three families, also of European ancestry. The variant was not enriched in the combined UK10K ASD cohorts of European ancestry but heterozygous GBE1 deletion was overrepresented in large ASD cohorts, collectively suggesting an association between GBE1 and ASD.

Relative predictive utility of the original and Autism-Specific Five-Minute Speech Samples for child behaviour problems in autistic preschoolers: A preliminary study.

LAY ABSTRACT: Parental Expressed Emotion refers to the intensity and nature of emotion shown when a parent talks about their child, and has been linked to child behaviour outcomes. Parental Expressed Emotion has typically been measured using the Five-Minute Speech Sample; however, the Autism-Specific Five-Minute Speech Sample was developed to better capture Expressed Emotion for parents of children on the autism spectrum. In each case, parents are asked to talk for 5 min about their child and how they get along with their child. Parents' statements are then coded for features such as number of positive and critical comments, or statements reflecting strong emotional involvement. While both the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample have been used with parents of autistic school-aged children, their relative usefulness for measuring Expressed Emotion in parents of preschool-aged children - including their links to child behaviour problems in this group - is unclear. We collected speech samples from 51 parents of newly diagnosed autistic preschoolers to investigate similarities and differences in results from the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample coding schemes. This included exploring the extent to which the Five-Minute Speech Sample and Autism-Specific Five-Minute Speech Sample, separately, or together, predicted current and future child behaviour problems. While the two measures were related, we found only the Autism-Specific Five-Minute Speech Sample - but not the Five-Minute Speech Sample - was related to child behavioural challenges. This adds support to the suggestion that the Autism-Specific Five-Minute Speech Sample may be a more useful measure of parental Expressed Emotion in this group, and provides a first step towards understanding how autistic children might be better supported by targeting parental Expressed Emotion.

Effect of Preemptive Intervention on Developmental Outcomes Among Infants Showing Early Signs of Autism: A Randomized Clinical Trial of Outcomes to Diagnosis.

Importance: Intervention for individuals with autism spectrum disorder (ASD) typically commences after diagnosis. No trial of an intervention administered to infants before diagnosis has shown an effect on diagnostic outcomes to date. Objective: To determine the efficacy of a preemptive intervention for ASD beginning during the prodromal period. Design, Setting, and Participants: This 2-site, single rater-blinded randomized clinical trial of a preemptive intervention vs usual care was conducted at 2 Australian research centers (Perth, Melbourne). Community sampling was used to recruit 104 infants aged 9 to 14 months showing early behaviors associated with later ASD, as measured by the Social Attention and Communication Surveillance-Revised. Recruitment occurred from June 9, 2016, to March 30, 2018. Final follow-up data were collected on April 15, 2020. Interventions: Infants were randomized on a 1:1 ratio to receive either a preemptive intervention plus usual care or usual care only over a 5-month period. The preemptive intervention group received a 10-session social communication intervention, iBASIS-Video Interaction to Promote Positive Parenting (iBASIS-VIPP). Usual care comprised services delivered by community clinicians. Main Outcomes and Measures: Infants were assessed at baseline (approximate age, 12 months), treatment end point (approximate age, 18 months), age 2 years, and age 3 years. Primary outcome was the combined blinded measure of ASD behavior severity (the Autism Observation Scale for Infants and the Autism Diagnostic Observation Schedule, second edition) across the 4 assessment points. Secondary outcomes were an independent blinded clinical ASD diagnosis at age 3 years and measures of child development. Analyses were preregistered and comprised 1-tailed tests with an α level of .05. Results: Of 171 infants assessed for eligibility, 104 were randomized; 50 infants (mean [SD] chronological age, 12.40 [1.93] months; 38 boys [76.0%]) received the iBASIS-VIPP preemptive intervention plus usual care (1 infant was excluded after randomization), and 53 infants (mean [SD] age, 12.38 [2.02] months; 32 boys [60.4%]) received usual care only. A total of 89 participants (45 in the iBASIS-VIPP group and 44 in the usual care group) were reassessed at age 3 years. The iBASIS-VIPP intervention led to a reduction in ASD symptom severity (area between curves, -5.53; 95% CI, -∞ to -0.28; P = .04). Reduced odds of ASD classification at age 3 years was found in the iBASIS-VIPP group (3 of 45 participants [6.7%]) vs the usual care group (9 of 44 participants [20.5%]; odds ratio, 0.18; 95% CI, 0-0.68; P = .02). Number needed to treat to reduce ASD classification was 7.2 participants. Improvements in caregiver responsiveness and language outcomes were also observed in the iBASIS-VIPP group. Conclusions and Relevance: Receipt of a preemptive intervention for ASD from age 9 months among a sample of infants showing early signs of ASD led to reduced ASD symptom severity across early childhood and reduced the odds of an ASD diagnosis at age 3 years. Trial Registration: http://anzctr.org.au identifier: ACTRN12616000819426.

The Evolution of Single-Cell Analysis and Utility in Drug Development.

This review provides a brief history of the advances of cellular analysis tools focusing on instrumentation, detection probes, and data analysis tools. The interplay of technological advancement and a deeper understanding of cellular biology are emphasized. The relevance of this topic to drug development is that the evaluation of cellular biomarkers has become a critical component of the development strategy for novel immune therapies, cell therapies, gene therapies, antiviral therapies, and vaccines. Moreover, recent technological advances in single-cell analysis are providing more robust cellular measurements and thus accelerating the advancement of novel therapies.Graphical abstract.

Bimodal expression of potential drug target CLL-1 (CLEC12A) on CD34+ blasts of AML patients.

OBJECTIVES: This study aims to retrospectively assess C-lectin-like molecule 1 (CLL-1) bimodal expression on CD34+ blasts in acute myeloid leukemia (AML) patients (total N = 306) and explore potential CLL-1 bimodal associations with leukemia and patient-specific characteristics. METHODS: Flow cytometry assays were performed to assess the deeper immunophenotyping of CLL-1 bimodality. Cytogenetic analysis was performed to characterize the gene mutation on CLL-1-negative subpopulation of CLL-1 bimodal AML samples. RESULTS: The frequency of a bimodal pattern of CLL-1 expression of CD34+ blasts ranged from 8% to 65% in the different cohorts. Bimodal CLL-1 expression was most prevalent in patients with MDS-related AML (P = .011), ELN adverse risk (P = .002), NPM1 wild type (WT, P = .049), FLT3 WT (P = .035), and relatively low percentages of leukemia-associated immunophenotypes (P = .006). Additional immunophenotyping analysis revealed the CLL-1- subpopulation may consist of pre-B cells, immature myeloblasts, and hematopoietic stem cells. Furthermore, (pre)-leukemic mutations were detected in both CLL-1+ and CLL-1- subfractions of bimodal samples (N = 3). CONCLUSIONS: C-lectin-like molecule 1 bimodality occurs in about 25% of AML patients and the CLL-1- cell population still contains malignant cells, hence it may potentially limit the effectiveness of CLL-1-targeted therapies and warrant further investigation.