Effective drug combinations in breast, colon and pancreatic cancer cells.

Combinations of anti-cancer drugs can overcome resistance and provide new treatments1,2. The number of possible drug combinations vastly exceeds what could be tested clinically. Efforts to systematically identify active combinations and the tissues and molecular contexts in which they are most effective could accelerate the development of combination treatments. Here we evaluate the potency and efficacy of 2,025 clinically relevant two-drug combinations, generating a dataset encompassing 125 molecularly characterized breast, colorectal and pancreatic cancer cell lines. We show that synergy between drugs is rare and highly context-dependent, and that combinations of targeted agents are most likely to be synergistic. We incorporate multi-omic molecular features to identify combination biomarkers and specify synergistic drug combinations and their active contexts, including in basal-like breast cancer, and microsatellite-stable or KRAS-mutant colon cancer. Our results show that irinotecan and CHEK1 inhibition have synergistic effects in microsatellite-stable or KRAS-TP53 double-mutant colon cancer cells, leading to apoptosis and suppression of tumour xenograft growth. This study identifies clinically relevant effective drug combinations in distinct molecular subpopulations and is a resource to guide rational efforts to develop combinatorial drug treatments.

Drug mechanism-of-action discovery through the integration of pharmacological and CRISPR screens.

Low success rates during drug development are due, in part, to the difficulty of defining drug mechanism-of-action and molecular markers of therapeutic activity. Here, we integrated 199,219 drug sensitivity measurements for 397 unique anti-cancer drugs with genome-wide CRISPR loss-of-function screens in 484 cell lines to systematically investigate cellular drug mechanism-of-action. We observed an enrichment for positive associations between the profile of drug sensitivity and knockout of a drug's nominal target, and by leveraging protein-protein networks, we identified pathways underpinning drug sensitivity. This revealed an unappreciated positive association between mitochondrial E3 ubiquitin-protein ligase MARCH5 dependency and sensitivity to MCL1 inhibitors in breast cancer cell lines. We also estimated drug on-target and off-target activity, informing on specificity, potency and toxicity. Linking drug and gene dependency together with genomic data sets uncovered contexts in which molecular networks when perturbed mediate cancer cell loss-of-fitness and thereby provide independent and orthogonal evidence of biomarkers for drug development. This study illustrates how integrating cell line drug sensitivity with CRISPR loss-of-function screens can elucidate mechanism-of-action to advance drug development.

A single subcutaneous dose of eprinomectin (Eprecis®) is effective against common gastrointestinal nematodes and lungworms in experimentally infected lactating goats.

BACKGROUND: The health and productivity of dairy goats continue to be impacted by gastrointestinal nematodes (GIN) and lungworms (LW). Eprinomectin (EPN) is frequently selected for treatment because it is generally effective and does not require a milk withdrawal period. However, some factors, such as lactation, can have an impact on EPN pharmacokinetics and potentially its efficacy. To evaluate whether this can alter the efficacy of Eprecis® 2%, an eprinomectin injectable solution, a study was performed in lactating goats using the dose currently registered in cattle, sheep and goats (0.2 mg/kg). METHODS: This study was a blinded, randomized, controlled trial performed according to the VICH guidelines. Eighteen (18) worm-free lactating goats were included and experimentally challenged on day 28 with a mixed culture of infective gastrointestinal and lung nematode larvae (Haemonchus contortus, Trichostrongylus colubriformis, Teladorsagia circumcincta, Dictyocaulus filaria). At D-1, fecal samples were collected to confirm patent infection in all animals. On D0, the goats were randomly allocated into two groups of nine goats; group 1 was treated with Eprecis® 2% at 0.2 mg/kg BW by subcutaneous injection, while group 2 remained untreated. Fecal samples for egg counts were collected from all animals on days 3, 5, 7, 9, 11 and 14. On D14, all goats were killed, and the abomasum, small intestine and lungs were removed, processed and subsampled to record the number and species of worms. RESULTS: The treatment was well tolerated. After treatment, the arithmetic mean FEC decreased in the treated group and remained < 5 EPG until the end of the study, while the arithmetic mean FEC in the control group remained > 849.0 EPG. At D14, goats in the treated group had very limited or zero total worm counts, whereas all animals from the control group had a high worm burden. The measured efficacy was 100.0% against H. contortus and T. colubriformis, 99.9% against T. circumcincta and 98.0% against D. filaria. CONCLUSIONS: Eprinomectin (Eprecis®, 20 mg/ml), administered at the label dose (0.2 mg/kg), is highly effective against gastrointestinal nematodes and lungworms in lactating goats.

A pan-cancer screen identifies drug combination benefit in cancer cell lines at the individual and population level.

Combining drugs can enhance their clinical efficacy, but the number of possible combinations and inter-tumor heterogeneity make identifying effective combinations challenging, while existing approaches often overlook clinically relevant activity. We screen one of the largest cell line panels (N = 757) with 51 clinically relevant combinations and identify responses at the level of individual cell lines and tissue populations. We establish three response classes to model cellular effects beyond monotherapy: synergy, Bliss additivity, and independent drug action (IDA). Synergy is rare (11% of responses) and frequently efficacious (>50% viability reduction), whereas Bliss and IDA are more frequent but less frequently efficacious. We introduce "efficacious combination benefit" (ECB) to describe high-efficacy responses classified as either synergy, Bliss, or IDA. We identify ECB biomarkers in vitro and show that ECB predicts response in patient-derived xenografts better than synergy alone. Our work here provides a valuable resource and framework for preclinical evaluation and the development of combination treatments.

Large-scale Pan-cancer Cell Line Screening Identifies Actionable and Effective Drug Combinations.

Oncology drug combinations can improve therapeutic responses and increase treatment options for patients. The number of possible combinations is vast and responses can be context-specific. Systematic screens can identify clinically relevant, actionable combinations in defined patient subtypes. We present data for 109 anticancer drug combinations from AstraZeneca's oncology small molecule portfolio screened in 755 pan-cancer cell lines. Combinations were screened in a 7 × 7 concentration matrix, with more than 4 million measurements of sensitivity, producing an exceptionally data-rich resource. We implement a new approach using combination Emax (viability effect) and highest single agent (HSA) to assess combination benefit. We designed a clinical translatability workflow to identify combinations with clearly defined patient populations, rationale for tolerability based on tumor type and combination-specific "emergent" biomarkers, and exposures relevant to clinical doses. We describe three actionable combinations in defined cancer types, confirmed in vitro and in vivo, with a focus on hematologic cancers and apoptotic targets. SIGNIFICANCE: We present the largest cancer drug combination screen published to date with 7 × 7 concentration response matrices for 109 combinations in more than 750 cell lines, complemented by multi-omics predictors of response and identification of "emergent" combination biomarkers. We prioritize hits to optimize clinical translatability, and experimentally validate novel combination hypotheses. This article is featured in Selected Articles from This Issue, p. 695.

Pan-cancer proteomic map of 949 human cell lines.

The proteome provides unique insights into disease biology beyond the genome and transcriptome. A lack of large proteomic datasets has restricted the identification of new cancer biomarkers. Here, proteomes of 949 cancer cell lines across 28 tissue types are analyzed by mass spectrometry. Deploying a workflow to quantify 8,498 proteins, these data capture evidence of cell-type and post-transcriptional modifications. Integrating multi-omics, drug response, and CRISPR-Cas9 gene essentiality screens with a deep learning-based pipeline reveals thousands of protein biomarkers of cancer vulnerabilities that are not significant at the transcript level. The power of the proteome to predict drug response is very similar to that of the transcriptome. Further, random downsampling to only 1,500 proteins has limited impact on predictive power, consistent with protein networks being highly connected and co-regulated. This pan-cancer proteomic map (ProCan-DepMapSanger) is a comprehensive resource available at https://cellmodelpassports.sanger.ac.uk.

Profile of Dogs' Breeders and Their Considerations on Female Reproduction, Maternal Care and the Peripartum Stress-An International Survey.

Dogs are part of many households worldwide and in recent years in some western countries, more and more people describe them as members of the family. The accurate number of dogs per household and the actual demand for puppies are hard to estimate correctly. The sources of dogs seem to be an important element to consider before acquiring a dog since some behavioural disorders are more likely observed in dogs coming from puppy mills and pet stores. Therefore, there is an increased need to better-know dog breeders, theirs believes and practices. To full-fill this objective, an online questionnaire in five different languages (English, German, Polish, Portuguese and Spanish) was sent to dog breeders. The survey intended to study the demographics of dog breeders and to understand their perception and practices about reproduction, maternal behaviour and management of the dam during the peripartum period. We were also interested to evaluate the occurrence and the impact of stress around parturition and how breeders deal with overstressed bitches and if they believe that motherly quality could have a later-on effect on the livelihood of the dog. Six hundred and sixty-eight respondents participated in the survey, mainly from Australia, Brazil, Canada, Germany, Portugal, Poland, Spain, United Kingdom, United States of America and non-listed country (reported as 'other' in the survey). A country effect was observed in relation to housing system, human interaction, the use of techniques to define breeding and whelping time and different methods to manage stress during the peripartum period. Considering the demographics of the responders, breeding activity is, in general, a family based activity with an effect of country. Use of progesterone levels to manage reproduction and pregnancy diagnosis by ultrasound were cited as common practice. In general, parturition takes place under human supervision. Peripartum period was perceived as a stressful moment with a difference in the way of addressing the problem based on the country but reassuring the bitch by increasing human presence was frequently described. Inappropriate maternal behaviour was observed by half of responders and if presented primiparous bitches and parturition by C-section were overrepresented. Puppies stayed with the dams from 4 weeks to 9 weeks and dog breeders from Spain, Poland and Portugal are keeping puppies with their mother the longest. Overall, poor maternal behaviour has an impact on puppies' cognitive development with German breeders being more convinced than their counterparts from Brazil and Spain.

The View of the French Dog Breeders in Relation to Female Reproduction, Maternal Care and Stress during the Peripartum Period.

In France, as in many other western countries, dogs are an important part of the society as pets or working animals. The exact demand for puppies in France is unknown, as is the proportion of dogs coming from different breeding sources. Nevertheless, the origin of puppies is important since young dogs from puppy mills and pet stores appear to be more likely to develop behavioral disorders. Puppies coming from responsible breeders, on the other hand, tend to be better adapted. In well-managed kennels, an explanation for these behavioral differences may be associated with greater contact of litters with the dam and humans. Another factor that might influence a dog's temperament and character is maternal behavior. Although recent studies have shown that the quality of maternal care in dogs is important, direct effects on the development of behavioral problems such as fearfulness or noise sensitivity are still controversial. To better understand the view of breeders, due to an increased interest in maternal care of dogs, an online questionnaire was developed to assess the dog breeders' profiles and to explore their perception of normal maternal and stress-related behaviors during the peripartum period. In addition, the management of the female during this critical time was queried. Three-hundred and forty-five French dog breeders, representing 91 breeds, completed the online survey. Considering the demographics of the responders, breeding activity in France is mostly family-based with 76% raising two breeds of dogs that produce, on average, five litters/year. Around 60% of the breeders use progesterone levels to determine breeding date. The whelping date is estimated using multiple criteria and most labors and deliveries happen under human supervision. The majority of behaviors associated to good maternal care are defined by the vast majority as being related to more attention of the bitch towards the puppies with the frequency of nursing and licking being important clues. Globally, the peripartum is perceived as a stressful period and to minimize stress and reassure the bitch the favored method used is increasing human presence. Problems related to maternal behavior were described, notably with primiparous bitches.

Influence of ADAPTIL® during the Weaning Period: A Double-Blinded Randomised Clinical Trial.

ADAPTIL®, a dog-appeasing pheromone, was shown to modify the dam-puppies' interactions during the neonatal period but could also influence the weaning period. Fourteen bitch/litter dyads continuously exposed to ADAPTIL® from the third/fourth weeks until the seventh/eighth weeks postpartum were compared to 11 dyads exposed to a placebo. Maternal and puppy behaviours were video-recorded, and at three time points (weeks three/four, weeks five/six and weeks seven/eight) after parturition. The well-being of the puppies and the overall relationship with the bitch were assessed using visual analogue scales (VAS) completed by the caregivers. All mothering behaviours, such as time of contact, licking and the amount of time dedicated to nursing puppies, decreased gradually from weeks three/four to weeks seven/eight. A switch in nursing position was observed over time: the use of the standing position increased compared to the lying position. The treatment had an effect on the nursing position: bitches in the ADAPTIL® group nursed more often in a lying (p = 0.007) or sitting position (p = 0.037), whereas for the placebo group, they favoured the standing position (p = 0.011). Once the puppies became more demanding for suckling, the bitches started showing rejection signs or aggressive growling, with a peak at weeks seven/eight. The pheromone seemed to reduce the intensity of avoidance in bitches exposed to ADAPTIL® at all time points. The score of all events combined as a sign of frustration showed a difference over the full period (p = 0.003), with the placebo group having a significantly higher score. From the caregiver perspective (through the VAS), under ADAPTIL®, the bitches were calmer when puppies tried to suckle (p = 0.001), more tolerant towards pups (p = 0.025), showed a greater motherly attitude (p = 0.016), the puppies cried less when left alone (p < 0.001) and interactions amongst pups were more harmonious (p = 0.055). Under ADAPTIL®, the bitches were less annoyed by the puppies, who seemed to cope better with frustration. The breeders perceived a benefit of the pheromone during the weaning period.

Conflict and affiliative behavior frequency between cats in multi-cat households: a survey-based study.

OBJECTIVES: The objective of this study was to collect information from cat owners about the frequency of conflict and affiliative signs in their households in order to: (1) assess correlations with the owners' ratings of household cat-cat harmony; and (2) determine if relationships exist between household variables, cat population variables and behavior frequencies. METHODS: Responses to an online survey of adult residents of the USA who were the primary caregiver of 2-4 indoor or indoor-outdoor cats were included in the analysis. Spearman's correlations and χ2 tests were used to compare behavior frequencies with household and cat population variables. RESULTS: Of 2492 owners of multiple cats, 73.3% noted conflict signs from the very beginning when introducing the cats. The more cats in the house, the more frequent the conflict signs. Staring was the most frequently observed conflict sign, occurring at least daily in 44.9% of households, followed, in order of decreasing frequency, by chasing, stalking, fleeing, tail twitching, hissing and wailing/screaming. Hissing occurred at least daily in 18% of households. Affiliative signs were observed more frequently than conflict signs. Physical contact between cats was observed at least daily in around half of the multi-cat households. Higher harmony scores were correlated with less frequent conflict signs and more frequent affiliative signs. No household or cat population variable, including home size or numerically adequate resources provision, was strongly predictive of the frequency of conflict or affiliative signs. CONCLUSIONS AND RELEVANCE: This is the first large-scale online survey to obtain frequencies of conflict and affiliative behaviors and compare them with factors linked to the cats or the home settings. The study confirmed that feline relationships are correlated with the owner's perceived impression of the initial introduction, but other household factors and cat population variables included in the study were not strongly predictive of the frequency of conflict or affiliative signs.

Influence of dog-appeasing pheromone on canine maternal behaviour during the peripartum and neonatal periods.

BACKGROUND: Parturition and the initial postpartum period are important moments in the reproductive cycle of dogs. METHODS: A study assessed the effect of ADAPTIL, a dog-appeasing pheromone, on maternal behaviour during peripartum. Bitches were continuously exposed to ADAPTIL (n=20) or placebo (n=21) in double-blinded conditions from an average of about seven days before parturition up to 21 days postpartum. Differences in maternal behaviour in relation to the treatment were evaluated by the observation of specific activities through video recordings, such as the time spent by the bitch in close contact with the puppies, oronasal interaction and nursing duration and position. Videos were recorded at four time points (W0: within the first 48 hours of whelping; W1: one week after parturition; W2: two weeks after parturition; and W3: three weeks after parturition). In addition, the perception of breeders in relation to the quality of maternal care, puppies' wellbeing and overall relationship between the bitches and the puppies was evaluated using Visual Analogue Scale at the same time points. Moreover, the daily activity of the bitches was measured by using an electronic device (FitBark dog activity trackers, Kansas City, Missouri). RESULTS: For all observed maternal behaviours, there was a steady decrease in levels as the puppies developed, independently of treatment. However, bitches exposed to ADAPTIL tended to nurse significantly more in lying position, while those exposed to the placebo nursed more in a seated position, especially at W1 (P=0.06) and W3 (P=0.005). According to the breeders, the attention scores of bitches towards puppies were significantly higher in ADAPTIL than in the placebo group at each time point (P=0.01). Moreover, a difference according to parity was observed (P=0.004), with greater attention score displayed by primiparous bitches exposed to ADAPTIL compared with placebo on W0 (P=0.02), W1 and W3 (P<0.001). The global mother-puppies relationship was also perceived as significantly better (P=0.0002) by breeders of bitches exposed to ADAPTIL, with significant differences at W2 (P=0.01) and W3 (P=0.001). The bitches' daily activity increased starting two days before the whelp, peaked during parturition and then gradually declined up until four days postpartum. There was a trend towards a difference in the activity level according to the treatment during the full study period (P=0.09) and at two days before parturition (P=0.07). Bitches exposed to ADAPTIL were more active compared with placebo in relation to the FitBark data. CONCLUSION: The use of ADAPTIL in maternity modulated maternal behaviours. Concerning the caregiver's view, bitches under the influence of ADAPTIL had greater and extended attention towards the puppies and they were eager to stay with the puppies for a longer time.

Evaluation of the efficacy of an appeasing pheromone diffuser product vs placebo for management of feline aggression in multi-cat households: a pilot study.

OBJECTIVES: Aggression and social tension among housemate cats is common and puts cats at risk of injury or relinquishment. The aim of this study was to evaluate the effectiveness of a new pheromone product in reducing aggression between housemate cats. METHODS: A new pheromone product (Feliway Friends) containing a proprietary cat-appeasing pheromone was evaluated for efficacy in reducing aggression between housemate cats via a randomized, double-blind, placebo-controlled pilot trial of 45 multi-cat households (pheromone [n = 20], placebo [n = 25]) reporting aggression for at least 2 weeks. Each household had 2-5 cats. Participants attended an educational training meeting on day (D) -7 and the veterinary behaviorist described behaviors to be monitored for 7 weeks using the Oakland Feline Social Interaction Scale (OFSIS), which assessed the frequency and intensity of 12 representative aggressive interactions. Participants were also provided with instructions for handling aggressive events, including classical conditioning, redirection by positive reinforcement and not punishing or startling the cat for aggressive displays. Punishment techniques were strongly discouraged. Plug-in diffusers with the pheromone product or placebo were utilized from D0-D28. Participants completed a daily diary of aggressive events and weekly OFSIS assessments through to D42. RESULTS: Evolution of the OFSIS-Aggression score according to treatment group in the full analysis set population revealed a significant effect on time and treatment group. The OFSIS-Aggression score decreased over time from D0-D28 in both groups (time factor P = 0.0001) with a significant difference in favor of the verum P = 0.06); similar results were found considering the D0-D42 period (time factor P = 0.0001 [D0] and P = 0.04 [D42]). CONCLUSIONS AND RELEVANCE: The OFSIS provided a quantifiable measure of the frequency and intensity of 12 intercat interactions reflecting conflict between cats. The cat-appeasing pheromone is a promising treatment for the management of aggression between housemate cats in multi-cat households.

The Origins and Vulnerabilities of Two Transmissible Cancers in Tasmanian Devils.

Transmissible cancers are clonal lineages that spread through populations via contagious cancer cells. Although rare in nature, two facial tumor clones affect Tasmanian devils. Here we perform comparative genetic and functional characterization of these lineages. The two cancers have similar patterns of mutation and show no evidence of exposure to exogenous mutagens or viruses. Genes encoding PDGF receptors have copy number gains and are present on extrachromosomal double minutes. Drug screening indicates causative roles for receptor tyrosine kinases and sensitivity to inhibitors of DNA repair. Y chromosome loss from a male clone infecting a female host suggests immunoediting. These results imply that Tasmanian devils may have inherent susceptibility to transmissible cancers and present a suite of therapeutic compounds for use in conservation.

Post-operative pain management: transition from epidural to oral analgesia.

Although managing pain in the acute surgical setting is a priority, there is a dearth of evidence to guide clinicians on how best to approach the discontinuation and transition of patients from epidural analgesia to oral analgesia post-operatively. This article describes an audit at a regional trust which examined data on patients' observations charts, as well as patients' self-reports of pain. The authors found that reducing epidural opioid concentrations post-operatively is useful in analgesic transition, using bupivacaine only for weaning has limited value, and that the timing of oral analgesia administration is important. They conclude that comprehensive pain assessment and better documentation are necessary to improve pain management practices. While the results demonstrate the advantage of reducing epidural opioid concentrations, decisions should be based on the needs of individual patients and not form part of a routine task.

Maternal distress and expressed emotion: cross-sectional and longitudinal relationships with behavior problems of children with intellectual disabilities.

Mothers of children with intellectual disability were assessed at two time points, 2 years apart (n = 75 at Time 1, n = 56 at Time 2). Data were gathered on maternal distress, mental health, expressed emotion, and the child's internalizing and externalizing behavior problems. Consistent with previous research with families of children who have intellectual disability, maternal distress and children's behavior problems entered into a bidirectional relationship over time. This relationship was found to be specific to externalizing problems. Exploratory analyses also suggest that maternal distress and depression had a bidirectional longitudinal relationship. In terms of maternal expressed emotion, criticism and not emotional over-involvement was cross-sectionally but not longitudinally related to children's externalizing behavior problems and to maternal distress.

Owner observations regarding cat scratching behavior: an internet-based survey.

OBJECTIVES: This study was performed to examine aspects of the cat, environment and scratching post that might influence scratching behavior, in an effort to determine how inappropriate scratching behavior might be refocused on acceptable targets. METHODS: An internet survey, posted on several public websites, gathered details about scratching behavior, as described by owners in their home environments, from 4331 respondents over a 4 month period. Responses from 39 different countries were analyzed, mostly from the USA, Canada and the UK. RESULTS: Owners offered traditionally recommended scratching substrates including rope, cardboard, carpet and wood. Rope was most frequently used when offered, although carpet was offered most commonly. Most owners provided at least one scratching post; cats scratched the preferred substrate more often when the post was a simple upright type or a cat tree with two or more levels and at least 3 ft high. Narrower posts (base width ⩽3 ft) were used more often than wider posts (base width ⩾5 ft). Intact or neutered cats (males and females) were as likely to scratch inappropriately, and inappropriate scratching decreased with age. Geriatric cats between the ages of 10 and 14 years preferred carpet substrate most frequently; all other ages preferred rope first. Inappropriate scratching decreased as the different types/styles of posts increased in the home. Inappropriate scratching did not increase if the number of cats or dogs increased in the household. Declawed cats were preventatively declawed most often to prevent household item destruction. CONCLUSIONS AND RELEVANCE: Although cats can have individual preferences, our data provide a starting point for veterinarians recommending scratching posts to clients.

Improving the feline veterinary consultation: the usefulness of Feliway spray in reducing cats' stress.

OBJECTIVES: Going to the veterinary clinic is a stressful experience for most cats as they feel threatened when entering a new and confined environment. The aim of this research was to investigate if Feliway spray, when used on the table in the consultation room, can decrease cats' stress and ease their handling. METHODS: A randomised, double-blind, placebo-controlled clinical trial was developed, using a total sample of 87 cats of both sexes, castrated or intact, of any breed, aged >26 weeks. A Feliway spray and a placebo solution spray were tested in two different consultation rooms. During the first phase, Feliway spray was applied to the examination table of one room and the placebo spray in the other. After a washout period of 15 days the spray allocation was switched. After the first 15 mins of general questioning and physical examination carried out by the veterinarian, the observer assessed the stress levels of the cats based on a seven-level 'cat stress score', and the ease of handling based on a five-point 'scale of handling' developed by the authors. RESULTS: The study demonstrated that the use of Feliway spray leads to significant (P = 0.01) differences in cats' usual behaviour, according to their owners. With regard to stress, animals exposed to Feliway spray showed significantly lower stress levels than those treated with placebo (P = 0.02). Regarding the scale of handling, the scoring did not differ significantly between cats under the effect of Feliway spray and cats receiving placebo (P = 0.01). CONCLUSIONS AND RELEVANCE: This research shows that the use of Feliway spray on the examination table improves the welfare of cats by reducing their stress during veterinary consultations. Feliway spray significantly changed the behaviour of the cats in this study, and offers a simple and effective way to help decrease stress in cats during the consultation.

Symptoms of ADHD and their correlates in children with intellectual disabilities.

Existing research suggests that children with intellectual disabilities are at increased risk for ADHD, and that the symptoms of the disorder might successfully be treated with stimulant drugs. However, there has been little exploration of ADHD symptoms and their correlates in children with intellectual disabilities. Analyses of three samples of children with intellectual disabilities are presented (total N=338). Correlational analyses showed that younger children, and those with a diagnosis of Autism were rated as having more ADHD/hyperactivity symptoms. There was little evidence of a sex difference, and no strong associations with domains of adaptive behavior (socialization, communication, and daily living skills). However, there was a small but significant negative association between mental age and ratings of symptoms. Finally, an increased prevalence of ADHD/hyperactivity symptoms was confirmed in the children with intellectual disabilities compared to their siblings. This effect remained after controlling for chronological and mental age differences between the siblings. These findings support those from previous research and suggest that ADHD/Hyperkinesis may be a valid psychiatric diagnosis for children with intellectual disabilities. However, a great deal more research is needed to explore the phenomenology of ADHD in intellectual disability and to develop an evidence base for psychosocial intervention.