DNA damage response defects in hematologic malignancies: mechanistic insights and therapeutic strategies

The DNA damage response (DDR) encompasses the detection and repair of DNA lesions and is fundamental to the maintenance of genome integrity. Germline DDR alterations underlie hereditary chromosome instability syndromes by promoting the acquisition of pathogenic structural variants in hematopoietic cells, resulting in increased predisposition to hematologic malignancies. Also frequent in hematologic malignancies are somatic mutations of DDR genes, typically arising from replication stress triggered by oncogene activation or deregulated tumor proliferation that provides a selective pressure for DDR loss. These defects impair homology-directed DNA repair or replication stress response, leading to an excessive reliance on error-prone DNA repair mechanisms that results in genomic instability and tumor progression. In hematologic malignancies, loss-of-function DDR alterations confer clonal growth advantage and adverse prognostic impact, but may also provide therapeutic opportunities. Selective targeting of functional dependencies arising from these defects could achieve synthetic lethality, a therapeutic concept exemplified by inhibition of poly(ADP-ribose) polymerase or the ATR-CHK1-WEE1 axis in malignancies harboring the BRCAness phenotype or genetic defects that increase replication stress. Furthermore, the role of DDR defects as a source of tumor immunogenicity, as well as their impact on the crosstalk between DDR, inflammation and tumor immunity are increasingly recognized, thus providing rationale for combining DDR modulation with immune modulation. The nature of the DDR-immune interface and the cellular vulnerabilities conferred by DDR defects may nonetheless be disease-specific and remain incompletely understood in many hematologic malignancies. Their comprehensive elucidation will be critical for optimizing therapeutic strategies to target DDR defects in these diseases.

Clonal Evolution of High-Risk Chronic Lymphocytic Leukemia: A Contemporary Perspective

Clonal evolution represents the natural process through which cancer cells continuously search for phenotypic advantages that enable them to develop and expand within microenvironmental constraints. In chronic lymphocytic leukemia (CLL), clonal evolution underpins leukemic progression and therapeutic resistance, with differences in clonal evolutionary dynamics accounting for its characteristically diverse clinical course. The past few years have witnessed profound changes in our understanding of CLL clonal evolution, facilitated by a maturing definition of high-risk CLL and an increasing sophistication of next-generation sequencing technology. In this review, we offer a modern perspective on clonal evolution of high-risk CLL, highlighting recent discoveries, paradigm shifts and unresolved questions. We appraise recent advances in our understanding of the molecular basis of CLL clonal evolution, focusing on the genetic and non-genetic sources of intratumoral heterogeneity, as well as tumor-immune dynamics. We review the technological innovations, particularly in single-cell technology, which have fostered these advances and represent essential tools for future discoveries. In addition, we discuss clonal evolution within several contexts of particular relevance to contemporary clinical practice, including the settings of therapeutic resistance to CLL targeted therapy and immunotherapy, as well as Richter transformation of CLL to high-grade lymphoma.

Targeting the p53 Pathway in CLL: State of the Art and Future Perspectives

The p53 pathway is a desirable therapeutic target, owing to its critical role in the maintenance of genome integrity. This is exemplified in chronic lymphocytic leukemia (CLL), one of the most common adult hematologic malignancies, in which functional loss of p53 arising from genomic aberrations are frequently associated with clonal evolution, disease progression, and therapeutic resistance, even in the contemporary era of CLL targeted therapy and immunotherapy. Targeting the 'undruggable' p53 pathway therefore arguably represents the holy grail of cancer research. In recent years, several strategies have been proposed to exploit p53 pathway defects for cancer treatment. Such strategies include upregulating wild-type p53, restoring tumor suppressive function in mutant p53, inducing synthetic lethality by targeting collateral genome maintenance pathways, and harnessing the immunogenicity of p53 pathway aberrations. In this review, we will examine the biological and clinical implications of p53 pathway defects, as well as our progress towards development of therapeutic approaches targeting the p53 pathway, specifically within the context of CLL. We will appraise the opportunities and pitfalls associated with these therapeutic strategies, and evaluate their place amongst the array of new biological therapies for CLL.

The use of continuous electronic prescribing data to infer trends in antimicrobial consumption and estimate the impact of stewardship interventions in hospitalized children

Background

Understanding antimicrobial consumption is essential to mitigate the development of antimicrobial resistance, yet robust data in children are sparse and methodologically limited. Electronic prescribing systems provide an important opportunity to analyse and report antimicrobial consumption in detail.

Objectives

We investigated the value of electronic prescribing data from a tertiary children’s hospital to report temporal trends in antimicrobial consumption in hospitalized children and compare commonly used metrics of antimicrobial consumption.

Methods

Daily measures of antimicrobial consumption [days of therapy (DOT) and DDDs] were derived from the electronic prescribing system between 2010 and 2018. Autoregressive moving-average models were used to infer trends and the estimates were compared with simulated point prevalence surveys (PPSs).

Results

More than 1.3 million antimicrobial administrations were analysed. There was significant daily and seasonal variation in overall consumption, which reduced annually by 1.77% (95% CI 0.50% to 3.02%). Relative consumption of meropenem decreased by 6.6% annually (95% CI −3.5% to 15.8%) following the expansion of the hospital antimicrobial stewardship programme. DOT and DDDs exhibited similar trends for most antimicrobials, though inconsistencies were observed where changes to dosage guidelines altered consumption calculation by DDDs, but not DOT. PPS simulations resulted in estimates of change over time, which converged on the model estimates, but with much less precision.

Conclusions

Electronic prescribing systems offer significant opportunities to better understand and report antimicrobial consumption in children. This approach to modelling administration data overcomes the limitations of using interval data and dispensary data. It provides substantially more detailed inferences on prescribing patterns and the potential impact of stewardship interventions.

Cancer and COVID-19: On the Quest for Effective Vaccines

Cancer vaccine development has been historically fraught with difficulty, but tremendous progress has been made over the past 5 years. In this In Focus article, we reflect on the progress and challenges with vaccine development for cancers in general and for hematologic malignancies in particular, and suggest how our cancer vaccine experience can offer insight into COVID-19 vaccination.

Integrative analysis of spontaneous CLL regression highlights genetic and microenvironmental interdependency in CLL

Spontaneous regression is a recognized phenomenon in chronic lymphocytic leukemia (CLL) but its biological basis remains unknown. We undertook a detailed investigation of the biological and clinical features of 20 spontaneous CLL regression cases incorporating phenotypic, functional, transcriptomic, and genomic studies at sequential time points. All spontaneously regressed tumors were IGHV-mutated with no restricted IGHV usage or B-cell receptor (BCR) stereotypy. They exhibited shortened telomeres similar to nonregressing CLL, indicating prior proliferation. They also displayed low Ki-67, CD49d, cell-surface immunoglobulin M (IgM) expression and IgM-signaling response but high CXCR4 expression, indicating low proliferative activity associated with poor migration to proliferation centers, with these features becoming increasingly marked during regression. Spontaneously regressed CLL displayed a transcriptome profile characterized by downregulation of metabolic processes as well as MYC and its downstream targets compared with nonregressing CLL. Moreover, spontaneous regression was associated with reversal of T-cell exhaustion features including reduced programmed cell death 1 expression and increased T-cell proliferation. Interestingly, archetypal CLL genomic aberrations including HIST1H1B and TP53 mutations and del(13q14) were found in some spontaneously regressing tumors, but genetic composition remained stable during regression. Conversely, a single case of CLL relapse following spontaneous regression was associated with increased BCR signaling, CLL proliferation, and clonal evolution. These observations indicate that spontaneously regressing CLL appear to undergo a period of proliferation before entering a more quiescent state, and that a complex interaction between genomic alterations and the microenvironment determines disease course. Together, the findings provide novel insight into the biological processes underpinning spontaneous CLL regression, with implications for CLL treatment.

Long-Term Ibrutinib Therapy Reverses CD8+ T Cell Exhaustion in B Cell Chronic Lymphocytic Leukaemia

Chronic Lymphocytic Leukaemia (CLL) is associated with immune suppression and susceptibility to infection. CD8+ T cell numbers are increased and demonstrate elevated expression of PD-1 and impaired function. The mechanisms driving these features of exhaustion are uncertain but are likely to include chronic immune recognition of tumor and/or infectious agents. We investigated the number, phenotype and function of total and virus-specific CD8+ T cells in 65 patients with CLL and 14 patients undergoing long-term ibrutinib therapy (median 21 months). Ibrutinib substantially reduced the number of both CD3+ T cells and CD8+ T cells. Importantly, this was associated with a reduction in PD-1 expression on CD8+ T cells (median 28 vs. 24%; p = 0.042) and 3.5 fold increase in cytokine production following mitogen stimulation. The influence of ibrutinib on antigen-specific CD8+ T cell function was assessed by HLA-peptide tetramers and revealed increased IFNγ and TNFα cytokine responses following stimulation with CMV or EBV peptides together with a 55% reduction in the frequency of "inflated" virus-specific CD8+ T cells. These findings reveal that long-term ibrutinib therapy is associated with substantial reversal of T cell exhaustion in B-CLL and is likely to contribute to the reduced infection risk seen in association with this agent.

Dynamic changes in clonal cytogenetic architecture during progression of chronic lymphocytic leukemia in patients and patient-derived murine xenografts

Subclonal heterogeneity and clonal selection influences disease progression in chronic lymphocytic leukemia (CLL). It is therefore important that therapeutic decisions are made based on an understanding of the CLL clonal architecture and its dynamics in individual patients. Identification of cytogenetic abnormalities by FISH remains the cornerstone of contemporary clinical practice and provides a simple means for prognostic stratification. Here, we demonstrate that multiplexed-FISH can enhance recognition of CLL subclonal repertoire and its dynamics during disease progression, both in patients and CLL patient-derived xenografts (PDX). We applied a combination of patient-specific FISH probes to 24 CLL cases before treatment and at relapse, and determined putative ancestral relationships between subpopulations with different cytogenetic features. We subsequently established 7 CLL PDX models in NOD/Shi-SCID/IL-2Rγctm1sug/Jic (NOG) mice. Application of multiplexed-FISH to these models demonstrated that all of the identified cytogenetic subpopulations had leukemia propagating activity and that changes in their representation during disease progression could be spontaneous, accelerated by treatment or treatment-induced. We conclude that multiplexed-FISH in combination with PDX models have the potential to distinguish between spontaneous and treatment-induced clonal selection, and therefore provide a valuable tool for the pre-clinical evaluation of novel therapies.

Reduction of biological response modifiers in the supernatant of washed paediatric red blood cells

BACKGROUND

Washing of red blood cells (RBC) can reduce unwanted biological response modifiers (BRMs) that can mediate transfusion complications in infants. The aim of this study was to examine the in vitro quality and the changes in BRMs following washing in paediatric RBC units.

MATERIALS AND METHODS

A pool and split design was used to prepare RBC (either 1 or 4 days old; n = 26 pairs). One unit was washed with 0·9% saline by centrifugation and then resuspended in SAG-M, while the other remained unwashed. Each RBC unit was divided to produce four units of paediatric-sized components. Samples were taken after 3 h and subsequently on days 1, 2, 7 and 14 post-wash.

RESULTS

Washing of RBC resulted in some red cell loss, with a minor increase in haemolysis. Washing effectively reduced supernatant potassium and IgA, as well as cytokines and complement proteins. RBC microparticles were significantly reduced in RBC washed at 1, but not 4 days post-collection. Incubation with supernatant from unwashed but not washed RBC led to endothelial cell activation, with increased cell surface expression of CD62E (E-selectin) and CD106 (VCAM).

CONCLUSION

Although washing affected some aspects of the in vitro quality of RBC, it effectively reduced the concentration and activity of BRMs in the supernatant of RBC. Such a reduction may be clinically beneficial in selected patient groups.

ATR inhibition induces synthetic lethality and overcomes chemoresistance in TP53- or ATM-defective chronic lymphocytic leukemia cells

TP53 and ataxia telangiectasia mutated (ATM) defects are associated with genomic instability, clonal evolution, and chemoresistance in chronic lymphocytic leukemia (CLL). Currently, therapies capable of providing durable remissions in relapsed/refractory TP53- or ATM-defective CLL are lacking. Ataxia telangiectasia and Rad3-related (ATR) mediates response to replication stress, the absence of which leads to collapse of stalled replication forks into chromatid fragments that require resolution through the ATM/p53 pathway. Here, using AZD6738, a novel ATR kinase inhibitor, we investigated ATR inhibition as a synthetically lethal strategy to target CLL cells with TP53 or ATM defects. Irrespective of TP53 or ATM status, induction of CLL cell proliferation upregulated ATR protein, which then became activated in response to replication stress. In TP53- or ATM-defective CLL cells, inhibition of ATR signaling by AZD6738 led to an accumulation of unrepaired DNA damage, which was carried through into mitosis because of defective cell cycle checkpoints, resulting in cell death by mitotic catastrophe. Consequently, AZD6738 was selectively cytotoxic to both TP53- and ATM-defective CLL cell lines and primary cells. This was confirmed in vivo using primary xenograft models of TP53- or ATM-defective CLL, where treatment with AZD6738 resulted in decreased tumor load and reduction in the proportion of CLL cells with such defects. Moreover, AZD6738 sensitized TP53- or ATM-defective primary CLL cells to chemotherapy and ibrutinib. Our findings suggest that ATR is a promising therapeutic target for TP53- or ATM-defective CLL that warrants clinical investigation.

Preparation of red blood cell concentrates and plasma units from whole blood held overnight using a hollow-fibre separation system

BACKGROUND

The ErySep system represents an alternative to centrifuge-based whole blood (WB) separation, using gravity and filtration through hollow-fibres (0·2 µm pore size) to produce red blood cell (RBC) and plasma components. The aim of this study was to characterise the quality of ErySep RBC and plasma units compared with standard products from WB held overnight.

METHODS/MATERIALS

Two ABO-compatible WB units (n = 24) were pooled and split to produce matched products. One of the WB units was separated into components using the ErySep system (ErySep; n = 12), whereas the other units were separated by centrifugation (control; n = 12). RBC units were stored at 2-6 °C and assessed for in vitro quality over 42 days of storage. Plasma was frozen at -30 °C and tested upon thawing.

RESULTS

Processing WB with the ErySep system took longer than controls. The ErySep RBC units were of an appropriate volume (307 ± 17 mL) and contained sufficient Hb (50 ± 2 g unit(-1) ). ErySep RBC components contained more microparticles relative to controls at expiry. The plasma volume, total protein, coagulation factor activity (fibrinogen, FV, FVIII) and number of microparticles was lower in the ErySep units compared with controls.

CONCLUSION

Following overnight hold of WB, the ErySep system was capable of producing RBC components that met specifications. However, the ErySep plasma components did not meet quality specifications.

Synthetic lethality in chronic lymphocytic leukaemia with DNA damage response defects by targeting the ATR pathway

BACKGROUND

DNA damage response (DDR) defects, particularly TP53 and biallelic ataxia telangiectasia mutated (ATM) aberrations, are associated with genomic instability, clonal evolution, and chemoresistance in chronic lymphocytic leukaemia (CLL). Therapies capable of providing long-term disease control in CLL patients with DDR defects are lacking. Using AZD6738, a novel ATR inhibitor, we investigated ATR pathway inhibition as a synthetically lethal strategy for targeting CLL cells with these defects.

METHODS

The effect of AZD6738 was assessed by western blotting and immunofluorescence of key DDR proteins. Cytotoxicity was assessed by CellTiter-Gloluminescence assay (Promega, Madison, WI, USA) and by propidium iodide exclusion. Primary CLL cells with biallelic TP53 or ATM inactivation were xenotransplanted into NOD/Shi-scid/IL-2Rγ mice. After treatment with AZD6738 or vehicle, tumour load was measured by flow cytometric analysis of infiltrated spleens, and subclonal composition by fluorescence in-situ hybridisation for 17p(TP53) or 11q(ATM) deletion.

FINDINGS

AZD6738 provided potent and specific inhibition of ATR signalling with compensatory activation of ATM/p53 pathway in cycling CLL cells in the presence of genotoxic stress. In p53 or ATM defective cells, AZD6738 treatment resulted in replication fork stalls and accumulation of unrepaired DNA damage, as evidenced by γH2AX and 53BP1 foci formation, which was carried through into mitosis, resulting in cell death by mitotic catastrophe. AZD6738 displayed selective cytotoxicity towards ATM or p53 deficient CLL cells, and was highly synergistic in combination with cytotoxic chemotherapy. This finding was confirmed in primary xenograft models of DDR-defective CLL, where treatment with AZD6738 resulted in decreased tumour load and selective reduction of CLL subclones with ATM or TP53 alterations.

INTERPRETATION

We have provided mechanistic insight and demonstrated in-vitro and in-vivo efficacy of a novel therapeutic approach that specifically targets p53-null or ATM-null CLL cells. Such an approach can potentially help to avert clonal evolution, a major cause of therapeutic resistance and disease relapse.

FUNDING

Leukaemia & Lymphoma Research.

Field observations of time-place behaviour in scavenging birds

Encoding the spatial location and the time at which significant biological events occur is thought to be a fundamental way in which one form of memory is organized in animals (Gallistel, 1990, The Organization of Learning. MIT Press, Cambridge, MA). If this is true, one would expect to find evidence of this process in a wide variety of animals and in a wide number of situations. We report field observations of scavenging birds at two outdoor locations at which people tend to congregate and eat food, primarily around midday. Scavenging birds appeared to anticipate this peak in food availability and arrived at these locations before the number of people was at a maximum; time of day, not the absolute number of people, was the best predictor of the number of birds at both sites. At a third location where food is not consumed this relationship was not observed. Taken together these observations support the notion that animals represent the spatial and temporal characteristics of biologically important events and use this knowledge to forage efficiently.

Treatment with 4Jointz reduces knee pain over 12 weeks of treatment in patients with clinical knee osteoarthritis: a randomised controlled trial

OBJECTIVE

To assess the efficacy of thrice daily topical 4Jointz utilizing Acteev technology (a combination of a standardized comfrey extract and a pharmaceutical grade tannic acid, 3.5 g/day) on osteoarthritic knee pain, markers of inflammation and cartilage breakdown over 12 weeks.

PATIENTS AND METHODS

Adults aged 50-80 years (n = 133) with clinical knee OA were randomised to receive 4Jointz or placebo in addition to existing medications. Pain and function were measured using a visual analogue scale (VAS) and the Knee Injury and Osteoarthritis Outcome Score (KOOS) scale at baseline, 4, 8 and 12 weeks. Inflammation was measured analysing IL-6 expression and CTX-2 presence as representative for cartilage breakdown using ELISA, at baseline and 12 weeks.

RESULTS

Pain scores significantly reduced in the group who received 4Jointz compared to the group who received placebo after 12 weeks using both the VAS (-9.9 mm, P = 0.034) and the KOOS pain scale (+5.7, P = 0.047). Changes in IL-6 and CTX-2 were not significant (-0.04, P = 0.5; -0.01, P = 0.68). Post-hoc analyses suggested that treatment may be most effective in women (VAS -16.8 mm, P = 0.008) and those with milder radiographic osteoarthritis (OA) (VAS -16.1 mm, P = 0.009). Rates of adverse events were similar in both groups, excepting local rash that was more common amongst participants receiving 4Jointz (21% vs 1.6%, IRR 13.2, P = 0.013), but only 26% (n = 4) of participants with rashes discontinued treatment. There were no changes in systemic blood results.

CONCLUSIONS

Topical treatment using 4Jointz reduced pain but had no effect on inflammation or cartilage breakdown over 12 weeks of treatment.

TRIAL REGISTRATION

Australia and New Zealand Clinical Trials registry ACTRN12610000877088.

Monoclonal B-cell lymphocytosis and chronic lymphocytic leukemia

BACKGROUND

A diagnosis of chronic lymphocytic leukemia (CLL) requires a count of over 5000 circulating CLL-phenotype cells per cubic millimeter. Asymptomatic persons with fewer CLL-phenotype cells have monoclonal B-cell lymphocytosis (MBL). The goal of this study was to investigate the relation between MBL and CLL.

METHODS

We investigated 1520 subjects who were 62 to 80 years of age with a normal blood count and 2228 subjects with lymphocytosis (>4000 lymphocytes per cubic millimeter) for the presence of MBL, using flow cytometry. Monoclonal B cells were further characterized by means of cytogenetic and molecular analyses. A representative cohort of 185 subjects with CLL-phenotype MBL and lymphocytosis were monitored for a median of 6.7 years (range, 0.2 to 11.8).

RESULTS

Monoclonal CLL-phenotype B cells were detected in 5.1% of subjects (78 of 1520) with a normal blood count and 13.9% (309 of 2228) with lymphocytosis. CLL-phenotype MBL had a frequency of 13q14 deletion and trisomy 12 similar to that of CLL and showed a skewed repertoire of the immunoglobulin heavy variable group (IGHV) genes. Among 185 subjects presenting with lymphocytosis, progressive lymphocytosis occurred in 51 (28%), progressive CLL developed in 28 (15%), and chemotherapy was required in 13 (7%). The absolute B-cell count was the only independent prognostic factor associated with progressive lymphocytosis. During follow-up over a median of 6.7 years, 34% of subjects (62 of 185) died, but only 4 of these deaths were due to CLL. Age above 68 years and hemoglobin level below 12.5 g per deciliter were the only independent prognostic factors for death.

CONCLUSIONS

The CLL-phenotype cells found in the general population and in subjects with lymphocytosis have features in common with CLL cells. CLL requiring treatment develops in subjects with CLL-phenotype MBL and with lymphocytosis at the rate of 1.1% per year.

Zoledronate inhibits proliferation and induces apoptosis of imatinib-resistant chronic myeloid leukaemia cells

Although imatinib mesylate has revolutionized the treatment of chronic myeloid leukaemia (CML), resistance to the drug, manifesting as relapse after an initial response or persistence of disease, remains a therapeutic challenge. In order to overcome this, alternative or additional targeting of signaling pathways downstream of Bcr-Abl may provide the best option for improving clinical response. Bisphosphonates, such as zoledronate, have been shown to inhibit the oncogenicity of Ras, an important downstream effector of Bcr-Abl. In this study, we show that zoledronate is equally effective in inhibiting the proliferation and clonogenicity of both imatinib-sensitive and -resistant CML cells, regardless of their mechanism of resistance. This is achieved by the induction of S-phase cell cycle arrest and apoptosis, through the inhibition of prenylation of Ras and Ras-related proteins by zoledronate. The combination of imatinib and zoledronate also augmented the activity of either drug alone and this occurred in imatinib-resistant CML cells as well. Since zoledronate is already available for clinical use, these results suggest that it may be an effective addition to the armamentarium of drugs for the treatment of CML.

Downstream effects on human low density lipoprotein of homocysteine exported from endothelial cells in an in vitro system

A model system is presented using human umbilical vein endothelial cells (HUVECs) to investigate the role of homocysteine (Hcy) in atherosclerosis. HUVECs are shown to export Hcy at a rate determined by the flux through the methionine/Hcy pathway. Additional methionine increases intracellular methionine, decreases intracellular folate, and increases Hcy export, whereas additional folate inhibits export. An inverse relationship exists between intracellular folate and Hcy export. Hcy export may be regulated by intracellular S-adenosyl methionine rather than by Hcy. Human LDLs exposed to HUVECs exporting Hcy undergo time-related lipid oxidation, a process inhibited by the thiol trap dithionitrobenzoate. This is likely to be related to the generation of hydroxyl radicals, which we show are associated with Hcy export. Although Hcy is the major oxidant, cysteine also contributes, as shown by the effect of glutamate. Finally, the LDL oxidized in this system showed a time-dependent increase in uptake by human macrophages, implying an upregulation of the scavenger receptor. These results suggest that continuous export of Hcy from endothelial cells contributes to the generation of extracellular hydroxyl radicals, with associated oxidative modification of LDL and incorporation into macrophages, a key step in atherosclerosis. Factors that regulate intracellular Hcy metabolism modulate these effects.

Ritanserin, a central 5-HT2 antagonist, in heavy social drinkers: desire to drink, alcohol intake and related effects

Ritanserin, a 5-HT2 receptor antagonist, decreased alcohol intake in some, but not all, animal studies and in an open clinical study. We tested the short-term effects of ritanserin in 39 (35 male, four female) heavy social drinkers (consuming at least 28 drinks/week), aged 19-63 years, who were not seeking treatment. After an intake assessment, they received placebo for 7 days in a single-blind baseline. They were then randomly assigned to one of three double-blind treatments for 14 days: ritanserin 5 mg/day (n = 12), ritanserin 10 mg/day (n = 13) or placebo (n = 14). Subjects recorded daily outpatient alcohol intake. Feelings of intoxication and interest, desire, craving and liking for alcohol were rated retrospectively at each weekly study visit. Experimental drinking sessions were conducted after baseline (EDS1) and treatment (EDS2); in each session subjects were offered 18 mini-drinks (total = six standard) and rated their desire to drink, intoxication and mood (POMS). Outpatient results: ritanserin 5 mg/day decreased desire and craving for alcohol (vs. baseline, p < 0.05) but not alcohol intake. Liking of alcohol decreased from baseline with ritanserin 10 mg/day (p = 0.01) and placebo (p = 0.05). Changes in alcohol intake from baseline with ritanserin 10 mg/day (increase, p > 0.05) and placebo (decrease, p > 0.05) were different (p < 0.05). EDS results: in EDS2, desire ratings for the first three mini-drinks were lower after ritanserin 5 mg/day than after ritanserin 10 mg/day (p < 0.05), but the decreases were not statistically significant when EDS1 desire ratings were controlled for. Ritanserin 10 mg/day increased alcohol-induced feelings of intoxication and friendliness, compared with placebo (p < 0.05). Both ritanserin 5 mg/day and 10 mg/day enhanced alcohol-induced decreases in fatigue, compared with placebo (p < 0.05). These results indicate that ritanserin may have differential effects on alcohol intake, desire, craving and liking, intoxication and some of alcohol's effects on mood. However, they suggest that ritanserin has limited efficacy in reducing alcohol intake in heavy drinkers.