Testing for medical school selection: What are prospective doctors' experiences and perceptions of the GAMSAT and what are the consequences of testing?

Written tests for selection into medicine have demonstrated reliability and there is accumulating evidence regarding their validity, but we know little about the broader impacts or consequences of medical school selection tests from the perspectives of key stakeholders. In this first Australian study of its kind, we use consequential validity as a theoretical lens to examine how medical school students and applicants view and experience the Graduate Medical Schools Admission Test (GAMSAT), and the consequences of testing. Participants (n = 447) were recruited from five graduate-entry medical schools across Australia and a publicly available online test preparation forum. An online survey was used to gather demographic information, and quantitative and qualitative data. Quantitative data were analysed via descriptive statistics and qualitative data were thematically analysed. The findings showed there was a considerable financial burden associated with preparing for and sitting the GAMSAT and moderate agreement regarding the GAMSAT as a fair selection method. The main unintended consequences of using the GAMSAT as a selection tool included barriers related to test affordability and language, and socialisation into the hidden curriculum of medicine. Selection tools such as the GAMSAT have some limitations when the goals are to support equitable participation in medicine and professional identity development. Our study highlights the value interpretive and theoretically-informed research in contributing to the evidence base on medical school selection.

A feasibility study of a novel low-level light therapy for digital ulcers in systemic sclerosis

Background: Locally acting, well-tolerated treatments for systemic sclerosis (SSc) digital ulcers (DUs) are needed.

Objectives: Our primary aim was to investigate the safety, feasibility, and tolerability of a novel low-level light therapy (LTTT). A secondary aim was to tentatively assess efficacy.

Methods: A custom-built device comprising infrared (850 nm), red (660 nm), and violet (405 nm) LEDs was utilized. DUs were irradiated with 10 J/cm² twice weekly for 3 weeks, with follow-up at weeks 4 and 8. Any safety concerns were documented. Patient opinion on time to deliver, feasibility, and pain visual analogue score (VAS; 0–100, 100 most severe) was collected. Patient and clinician DU global assessment VAS were documented. DUs were evaluated by laser Doppler perfusion imaging pre- and post-irradiation.

Results: In all, 14 DUs in eight patients received a total of 46 light exposures, with no safety concerns. All patients considered LTTT ‘took just the right amount of time’ and was ‘feasible’, with a low associated mean pain VAS of 1.6 (SD: 5.2). Patient and clinician global DC VAS improved during the study (mean change: –7.1 and –5.2, respectively, both p < .001). DU perfusion significantly increased post-irradiation.

Conclusions: LTTT for DUs is safe, feasible, and well tolerated. There was an early tentative suggestion of treatment efficacy.

Industrially-Scalable Microencapsulation of Plant Beneficial Bacteria in Dry Cross-Linked Alginate Matrix

Microencapsulation of plant-beneficial bacteria, such as pink pigmented facultative methylotrophs (PPFM), may greatly extend the shelf life of these Gram-negative microorganisms and facilitate their application to crops for sustainable agriculture. A species of PPFM designated Methylobacterium radiotolerans was microencapsulated in cross-linked alginate microcapsules (CLAMs) prepared by an innovative and industrially scalable process that achieves polymer cross-linking during spray-drying. PPFM survived the spray-drying microencapsulation process with no significant loss in viable population, and the initial population of PPFM in CLAMs exceeded 1010 CFU/g powder. The PPFM population in CLAMs gradually declined by 4 to 5 log CFU/g over one year of storage. The extent of alginate cross-linking, modulated by adjusting the calcium phosphate content in the spray-dryer feed, did not influence cell viability after spray-drying, viability over storage, or dry particle size. However, particle size measurements and light microscopy of aqueous CLAMs suggest that enhanced crosslinking may limit the release of encapsulated bacteria. This work demonstrates an industrially scalable method for producing alginate-based inoculants that may be suitable for on-seed or foliar spray applications.

Characterisation of a major phytoplankton bloom in the River Thames (UK) using flow cytometry and high performance liquid chromatography

Recent river studies have observed rapid phytoplankton dynamics, driven by diurnal cycling and short-term responses to storm events, highlighting the need to adopt new high-frequency characterisation methods to understand these complex ecological systems. This study utilised two such analytical methods; pigment analysis by high performance liquid chromatography (HPLC) and cell counting by flow cytometry (FCM), alongside traditional chlorophyll spectrophotometry and light microscopy screening, to characterise the major phytoplankton bloom of 2015 in the River Thames, UK. All analytical techniques observed a rapid increase in chlorophyll a concentration and cell abundances from March to early June, caused primarily by a diatom bloom. Light microscopy identified a shift from pennate to centric diatoms during this period. The initial diatom bloom coincided with increased HPLC peridinin concentrations, indicating the presence of dinoflagellates which were likely to be consuming the diatom population. The diatom bloom declined rapidly in early June, coinciding with a storm event. There were low chlorophyll a concentrations (by both HPLC and spectrophotometric methods) throughout July and August, implying low biomass and phytoplankton activity. However, FCM revealed high abundances of pico-chlorophytes and cyanobacteria through July and August, showing that phytoplankton communities remain active and abundant throughout the summer period. In combination, these techniques are able to simultaneously characterise a wider range of phytoplankton groups, with greater certainty, and provide improved understanding of phytoplankton functioning (e.g. production of UV inhibiting pigments by cyanobacteria in response to high light levels) and ecological status (through examination of pigment degradation products). Combined HPLC and FCM analyses offer rapid and cost-effective characterisation of phytoplankton communities at appropriate timescales. This will allow a more-targeted use of light microscopy to capture phytoplankton peaks or to investigate periods of rapid community succession. This will lead to greater system understanding of phytoplankton succession in response to biogeochemical drivers.

A Multicenter Study of the Validity and Reliability of Responses to Hand Cold Challenge as Measured by Laser Speckle Contrast Imaging and Thermography: Outcome Measures for Systemic Sclerosis-Related Raynaud's Phenomenon

OBJECTIVE

Reliable and objective outcome measures to facilitate clinical trials of novel treatments for systemic sclerosis (SSc)-related Raynaud's phenomenon (RP) are badly needed. Laser speckle contrast imaging (LSCI) and thermography are noninvasive measures of perfusion that have shown excellent potential. This multicenter study was undertaken to determine the reliability and validity of a hand cold challenge protocol using LSCI, standard thermography, and low-cost cell phone/mobile phone thermography (henceforth referred to as mobile thermography) in patients with SSc-related RP.

METHODS

Patients with RP secondary to SSc were recruited from 6 UK tertiary care centers. The patients underwent cold challenge on 2 consecutive days. Changes in cutaneous blood flow/skin temperature at each visit were imaged simultaneously using LSCI, standard thermography, and mobile thermography. Measurements included area under the curve (AUC) for reperfusion/rewarming and maximum blood flow rate/skin temperature after rewarming (MAX). Test-retest reliability was assessed using intraclass correlation coefficients (ICCs). Estimated latent correlations (estimated from multilevel models, taking values between -1 and 1; denoted as rho values) were used to assess the convergent validity of LSCI and thermography.

RESULTS

In total, 159 patients (77% with limited cutaneous SSc) were recruited (84% female, median age 63.3 years). LSCI and standard thermography both had substantial reliability, with ICCs for the reperfusion/rewarming AUC of 0.67 (95% confidence interval [95% CI] 0.54, 0.76) and 0.68 (95% CI 0.58, 0.80), respectively, and ICCs for the MAX of 0.64 (95% CI 0.52, 0.75) and 0.72 (95% CI 0.64, 0.81), respectively. Very high latent correlations were present for the AUCs of LSCI and thermography (ρ = 0.94; 95% CI 0.87, 1.00) and for the AUCs of standard and mobile thermography (ρ = 0.98; 95% CI 0.94, 1.00).

CONCLUSION

This is the first multicenter study to examine the reliability and validity of cold challenge using LSCI and thermography in patients with SSc-related RP. LSCI and thermography both demonstrated good potential as outcome measures. LSCI, standard thermography, and mobile thermography had very high convergent validity.

Reliability of digital ulcer definitions as proposed by the UK Scleroderma Study Group: A challenge for clinical trial design

Introduction

The reliability of clinician grading of systemic sclerosis-related digital ulcers has been reported to be poor to moderate at best, which has important implications for clinical trial design. The aim of this study was to examine the reliability of new proposed UK Scleroderma Study Group digital ulcer definitions among UK clinicians with an interest in systemic sclerosis.

Methods

Raters graded (through a custom-built interface) 90 images (80 unique and 10 repeat) of a range of digital lesions collected from patients with systemic sclerosis. Lesions were graded on an ordinal scale of severity: 'no ulcer', 'healed ulcer' or 'digital ulcer'.

Results

A total of 23 clinicians - 18 rheumatologists, 3 dermatologists, 1 hand surgeon and 1 specialist rheumatology nurse - completed the study. A total of 2070 (1840 unique + 230 repeat) image gradings were obtained. For intra-rater reliability, across all images, the overall weighted kappa coefficient was high (0.71) and was moderate (0.55) when averaged across individual raters. Overall inter-rater reliability was poor (0.15).

Conclusion

Although our proposed digital ulcer definitions had high intra-rater reliability, the overall inter-rater reliability was poor. Our study highlights the challenges of digital ulcer assessment by clinicians with an interest in systemic sclerosis and provides a number of useful insights for future clinical trial design. Further research is warranted to improve the reliability of digital ulcer definition/rating as an outcome measure in clinical trials, including examining the role for objective measurement techniques, and the development of digital ulcer patient-reported outcome measures.

Clinical effectiveness, cost-effectiveness and acceptability of low-intensity interventions in the management of obsessive-compulsive disorder: the Obsessive-Compulsive Treatment Efficacy randomised controlled Trial (OCTET)

BACKGROUND

The Obsessive-Compulsive Treatment Efficacy randomised controlled Trial emerged from a research recommendation in National Institute for Health and Care Excellence obsessive-compulsive disorder (OCD) guidelines, which specified the need to evaluate cognitive-behavioural therapy (CBT) treatment intensity formats.

OBJECTIVES

To determine the clinical effectiveness and cost-effectiveness of two low-intensity CBT interventions [supported computerised cognitive-behavioural therapy (cCBT) and guided self-help]: (1) compared with waiting list for high-intensity CBT in adults with OCD at 3 months; and (2) plus high-intensity CBT compared with waiting list plus high-intensity CBT in adults with OCD at 12 months. To determine patient and professional acceptability of low-intensity CBT interventions.

DESIGN

A three-arm, multicentre, randomised controlled trial.

SETTING

Improving Access to Psychological Therapies services and primary/secondary care mental health services in 15 NHS trusts.

PARTICIPANTS

Patients aged ≥ 18 years meeting Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition criteria for OCD, on a waiting list for high-intensity CBT and scoring ≥ 16 on the Yale-Brown Obsessive Compulsive Scale (indicative of at least moderate severity OCD) and able to read English.

INTERVENTIONS

Participants were randomised to (1) supported cCBT, (2) guided self-help or (3) a waiting list for high-intensity CBT.

MAIN OUTCOME MEASURES

The primary outcome was OCD symptoms using the Yale-Brown Obsessive Compulsive Scale - Observer Rated.

RESULTS

Patients were recruited from 14 NHS trusts between February 2011 and May 2014. Follow-up data collection was complete by May 2015. There were 475 patients randomised: supported cCBT (n = 158); guided self-help (n = 158) and waiting list for high-intensity CBT (n = 159). Two patients were excluded post randomisation (one supported cCBT and one waiting list for high-intensity CBT); therefore, data were analysed for 473 patients. In the short term, prior to accessing high-intensity CBT, guided self-help demonstrated statistically significant benefits over waiting list, but these benefits did not meet the prespecified criterion for clinical significance [adjusted mean difference -1.91, 95% confidence interval (CI) -3.27 to -0.55; p = 0.006]. Supported cCBT did not demonstrate any significant benefit (adjusted mean difference -0.71, 95% CI -2.12 to 0.70). In the longer term, access to guided self-help and supported cCBT, prior to high-intensity CBT, did not lead to differences in outcomes compared with access to high-intensity CBT alone. Access to guided self-help and supported cCBT led to significant reductions in the uptake of high-intensity CBT; this did not seem to compromise patient outcomes at 12 months. Taking a decision-making approach, which focuses on which decision has a higher probability of being cost-effective, rather than the statistical significance of the results, there was little evidence that supported cCBT and guided self-help are cost-effective at the 3-month follow-up compared with a waiting list. However, by the 12-month follow-up, data suggested a greater probability of guided self-help being cost-effective than a waiting list from the health- and social-care perspective (60%) and the societal perspective (80%), and of supported cCBT being cost-effective compared with a waiting list from both perspectives (70%). Qualitative interviews found that guided self-help was more acceptable to patients than supported cCBT. Professionals acknowledged the advantages of low intensity interventions at a population level. No adverse events occurred during the trial that were deemed to be suspected or unexpected serious events.

LIMITATIONS

A significant issue in the interpretation of the results concerns the high level of access to high-intensity CBT during the waiting list period.

CONCLUSIONS

Although low-intensity interventions are not associated with clinically significant improvements in OCD symptoms, economic analysis over 12 months suggests that low-intensity interventions are cost-effective and may have an important role in OCD care pathways. Further research to enhance the clinical effectiveness of these interventions may be warranted, alongside research on how best to incorporate them into care pathways.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN73535163.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 21, No. 37. See the NIHR Journals Library website for further project information.

Cost-effectiveness Analysis of Silver Delivery Approaches in the Management of Partial-thickness Burns

INTRODUCTION

Burn injury is a common type of traumatic injury that causes considerable morbidity and mortality, resulting in about 30,000 admissions annually in specialist burn centers and costing around $1 billion per year in the United States. One percent silver sulfadiazine has been utilized widely in the management of burns and newer silver dressings are on the market, including nanocrystalline silver dressings, silver-impregnated hydrofiber dressings, and silver-impregnated foam dressings.

OBJECTIVE

This study sought to determine the cost effectiveness of the newer silver dressings using clinical data from an indirect treatment comparison using silver sulfadiazine as the baseline.

MATERIALS AND METHODS

A decision analytic model was developed from a US payer's perspective for burn patients with a total body surface area of < 20%. Outcomes were length of stay, infections and incidence of surgical procedures, quality adjusted life years (QALYs), and cost.

RESULTS

The meta-analysis reported a statistically significant reduction in length of hospital stay and clinically important reductions in infections and incidence of surgical procedures in favor of the silver barrier dressing compared with other silver dressings. The estimated QALYs were 0.970 versus 0.969 versus 0.969 and mean cost per patient was $15,892, $23,799, and $24,269 for the nanocrystalline silver dressing, silver-impregnated hydrofiber dressing, and silver-impregnated foam dressing, respectively. The analysis showed the nanocrystalline silver dressing to be a dominant strategy (less costly with better outcomes). These findings were robust to a range of sensitivity analyses.

CONCLUSIONS

According to data from an indirect treatment comparison, this analysis suggests that nanocrystalline silver dressing is the most cost-effective silver delivery system. Prospective head-to-head research on the costs and outcomes of these silver delivery systems in this patient population is necessary to validate the results of this economic evaluation.

Abstract B171: PK/PD modeling of the first-in-class, potent and selective covalent CDK7 inhibitor, SY-1365, provides mechanistic basis for intermittent dosing regimens in preclinical efficacy models of hematologic and solid tumors

Introduction: CDK7 has recently emerged as an attractive gene control target in cancers driven by transcriptional dependencies, including triple-negative breast cancer (TNBC) and acute myeloid leukemia (AML). SY-1365 is a first-in-class, potent, and selective covalent CDK7 inhibitor that has shown durable and complete responses in xenograft models of AML and various solid tumors. To advance the development of this CDK7 inhibitor in patients, the current work assessed the relationship between SY-1365 pharmacokinetics (PK), pharmacodynamics (PD) measured as CDK7 target occupancy, and efficacy in mouse xenograft models of AML (HL-60) and TNBC (HCC70). Methods: SY-1365 was dosed intravenously in several xenograft experiments across a range of dose levels (5-40 mg/kg) and dose frequencies (daily to weekly). PK and changes in CDK7 occupancy were measured following single and repeat dosing, and efficacy studies measured the resultant dose-dependent changes in tumor volume over time after repeat dosing of SY-1365. To account for the temporal differences in PK, PD and tumor growth inhibition (TGI), a mathematical modeling approach was taken to integrate the resulting datasets. In addition, an assay to determine CDK7 occupancy in human PBMCs was developed to support the ongoing phase 1 study. Results: The PK in mouse was proportional with respect to dose and exhibited a terminal elimination half-life (t1/2) of 4 h. The PK/PD model was able to describe the PK, PD, and efficacy in HL-60 and HCC70 xenografts, with similar exposure and CDK7 occupancy profiles observed in these two xenografts. The model demonstrated a CDK7 turnover t1/2 of 69 h, longer than that reported for other oncogenic kinases targeted with covalent inhibitors where daily dosing is required (e.g., EGFRi, BTKi), with optimal efficacy achieved when target engagement was sustained over the dosing interval. This provides a mechanistic basis for intermittent dosing based on the dose-dependent TGI, including tumor regressions, observed with SY-1365 in in vivo models of TNBC and AML. Conclusions: The PK/PD relationship for target engagement and efficacy of the first-in-class potent and selective covalent CDK7 inhibitor, SY-1365, has been characterized in preclinical models through a mathematical modeling approach. Assays were developed to enable target occupancy quantification in xenograft tumors, and in human PBMCs as a surrogate tissue to support clinical investigation. Further investigations into tumor molecular profiles driving response are currently under way. In summary, this work supported the selection of an initial twice-weekly dosing regimen in the ongoing phase 1 trial of SY-1365 in adult patients with advanced solid tumors (NCT03134638).

Citation Format: Nigel J. Waters, Shanhu Hu, Brett Matzuka, Graeme Hodgson, Yixuan Ren, Yoon Choi, Kevin Dykstra, Christopher Roberts, Kevin Sprott, Emmanuelle di Tomaso, Christian Fritz. PK/PD modeling of the first-in-class, potent and selective covalent CDK7 inhibitor, SY-1365, provides mechanistic basis for intermittent dosing regimens in preclinical efficacy models of hematologic and solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B171.

A multicentre randomised assessment of the DAWN AC computer-assisted oral anticoagulant dosage program

Computer-assisted oral anticoagulant dosage is being increasingly used to meet growing demands for oral anticoagulation. The DAWN AC is one of the most widely used computer-dosage programs. Evidence of its value and that of other computer programs has been based previously only on laboratory evidence of “time in target INR range” (TIR) not on clinical safety in practice. A five-year international randomised clinical study of computer assistance with the DAWN AC program compared with manual dosage in 2,631 patients has been performed at 13 centres with established expertise in oral anticoagulation mainly in the EU. Safety assessment have been based on the comparison of bleeding or thrombotic events with DAWN AC compared with manual dosage in a randomised study. Safety of the DAWN AC program has been demonstrated. Clinical events of bleeding and thrombosis were almost identical with the experienced manual dosage group. Therapeutic control improved with DAWN AC to 66.8% from 63.4% TIR. The program failed to provide a dosage recommendation on only 5.7% of occasions. At a group of experienced centres with a special interest in oral anticoagulation, the DAWN AC computer-dosage program proved as safe clinically as manual dosage by experienced medical staff. With DAWN AC, laboratory control was improved, the difference being highly significant. The results should reassure hospitals and community clinics that the DAWN AC program is safe and facilitate greater and longer provision of warfarin treatment where required.

Comparison of Kaposi Sarcoma Risk in Human Immunodeficiency Virus-Positive Adults Across 5 Continents: A Multiregional Multicohort Study

BACKGROUND

We compared Kaposi sarcoma (KS) risk in adults who started antiretroviral therapy (ART) across the Asia-Pacific, South Africa, Europe, Latin, and North America.

METHODS

We included cohort data of human immunodeficiency virus (HIV)-positive adults who started ART after 1995 within the framework of 2 large collaborations of observational HIV cohorts. We present incidence rates and adjusted hazard ratios (aHRs).

RESULTS

We included 208140 patients from 57 countries. Over a period of 1066572 person-years, 2046 KS cases were diagnosed. KS incidence rates per 100000 person-years were 52 in the Asia-Pacific and ranged between 180 and 280 in the other regions. KS risk was 5 times higher in South African women (aHR, 4.56; 95% confidence intervals [CI], 2.73-7.62) than in their European counterparts, and 2 times higher in South African men (2.21; 1.34-3.63). In Europe, Latin, and North America KS risk was 6 times higher in men who have sex with men (aHR, 5.95; 95% CI, 5.09-6.96) than in women. Comparing patients with current CD4 cell counts ≥700 cells/µL with those whose counts were <50 cells/µL, the KS risk was halved in South Africa (aHR, 0.53; 95% CI, .17-1.63) but reduced by ≥95% in other regions.

CONCLUSIONS

Despite important ART-related declines in KS incidence, men and women in South Africa and men who have sex with men remain at increased KS risk, likely due to high human herpesvirus 8 coinfection rates. Early ART initiation and maintenance of high CD4 cell counts are essential to further reducing KS incidence worldwide, but additional measures might be needed, especially in Southern Africa.

Quantitative outcome measures for systemic sclerosis-related Microangiopathy - Reliability of image acquisition in Nailfold Capillaroscopy

BACKGROUND

Nailfold capillaroscopic parameters hold increasing promise as outcome measures for clinical trials in systemic sclerosis (SSc). Their inclusion as outcomes would often naturally require capillaroscopy images to be captured at several time points during any one study. Our objective was to assess repeatability of image acquisition (which has been little studied), as well as of measurement.

METHOD

41 patients (26 with SSc, 15 with primary Raynaud's phenomenon) and 10 healthy controls returned for repeat high-magnification (300×) videocapillaroscopy mosaic imaging of 10 digits one week after initial imaging (as part of a larger study of reliability). Images were assessed in a random order by an expert blinded observer and 4 outcome measures extracted: (1) overall image grade and then (where possible) distal vessel locations were marked, allowing (2) vessel density (across the whole nailfold) to be calculated (3) apex width measurement and (4) giant vessel count. Intra-rater, intra-visit and intra-rater inter-visit (baseline vs. 1week) reliability were examined in 475 and 392 images respectively. A linear, mixed-effects model was used to estimate variance components, from which intra-class correlation coefficients (ICCs) were determined.

RESULTS

Intra-visit and inter-visit reliability estimates (ICCs) were (respectively): overall image grade, 0.97 and 0.90; vessel density, 0.92 and 0.65; mean vessel width, 0.91 and 0.79; presence of giant capillary, 0.68 and 0.56. These estimates were conditional on each parameter being measurable.

CONCLUSION

Within-operator image analysis and acquisition are reproducible. Quantitative nailfold capillaroscopy, at least with a single observer, provides reliable outcome measures for clinical studies including randomised controlled trials.

Novel outreach settings to enhance sexually transmitted infection/HIV awareness, diagnosis and treatment in hard-to-reach populations

Despite recent rises in the number of cases of sexually transmitted infections (STIs) such as syphilis and gonorrhoea in England and increasing rates of HIV diagnosis among several men who have sex with men populations, many individuals are still not engaging with sexual health services. The John Hunter Clinic for Sexual Health, Chelsea and Westminster Hospital, London set up outreach clinics at the two world's largest adult lifestyle exhibitions in 2013 and 2015. This was the first time that a sexual health screening and promotion service was available at these large-scale (over 10,000 attendees at each) adult lifestyle events. A total of 381 individuals underwent STI screening across the two events. Nineteen (5.0%) patients were diagnosed with an infection. Twelve (3.1%) patients with Chlamydia trachomatis, three (0.8%) patients with syphilis, one (0.3%) patient with Neisseria gonorrhoeae, one (0.3%) patient with HIV, one (0.3%) patient with hepatitis B and one (0.3%) patient with hepatitis C. All 19 patients were promptly contacted with their results and had arrangements made for treatment or were referred for specialist follow up. Where possible, contact tracing was also performed. Implementing such outreach-based projects is challenged by lack of on-site laboratory support, high staffing demands and potentially high costs. However, we achieved a total HIV screening uptake rate of 94.5% amongst our outreach clinic attendees (versus 67% nationally in conventional sexual health clinic attendees) with an HIV positivity rate of 0.3% (versus 0.2% nationally in high HIV prevalence band populations). Additionally, 30.7% had never been tested for HIV previously (versus 20.7% nationally). Our work demonstrates that these strategies can help to address issues related to lack of STI/HIV screening in hard-to-reach populations and promote risk reduction behaviour.

Abstract 1143: Targeting the transcriptional kinases CDK12 and CDK13 in breast and ovarian cancer

CDK12 and CDK13 regulate expression of large transcripts requiring substantial processing to produce mature mRNA. This transcriptional regulation includes coordinated phosphorylation of specific repeats within the C-terminal domain of RNA polymerase II and association with RNA processing factors (Chila, 2016). RNAi knockdown of CDK12 in cell culture decreases expression of DNA damage response genes, including BRCA1 and ATR, while enhancing sensitivity to DNA damaging agents (Blazek, 2011; Liang, 2015). Recently THZ531, a selective covalent inhibitor of CDK12 and CDK13, was shown to decrease expression of DNA damage response genes in cell culture (Zhang, 2016). Here we present further studies with THZ531 to guide our discovery program toward molecules suitable for clinical development and to explore mechanistic rationales for combining a CDK12/13 inhibitor with PARP inhibitors or DNA damaging agents for difficult-to-treat cancers such as high-grade serous ovarian cancer and triple-negative breast cancer. Using THZ531 as a benchmark, we developed assays capable of discriminating sub-nM inhibitors, including quantifying time-dependent covalent inhibition and cell-based CDK occupancy. Since CDK7, like CDK12 and CDK13, contains a cysteine residue proximal to the kinase active site, these approaches are critical to understand covalent inhibitor selectivity. Furthermore, we performed kinome paneling studies to better understand selectivity of this scaffold in support of our ongoing efforts to optimize CDK12/13 potency and selectivity. To pharmacologically investigate the previously reported effects of CDK12 RNAi, growth inhibition of a panel of ovarian and breast cancer cell lines was assessed following treatment with THZ531 (OVA EC50 = 50-200 nM (n=6); BRCA EC50 &lt;50 nM (n=4)). Expression profiling revealed that THZ531 treatment resulted in different sets of genes being affected than was observed following treatment with inhibitors targeting CDK7, CDK9 or BET-bromodomain proteins. Additionally, CDK12/13, CDK7 and CDK9 inhibitors were profiled in a broad cell line panel (n&gt;400) to reveal relationships between inhibitor sensitivity, mutation status, gene expression, and potential oncology indications that may be addressed by these different mechanisms. Finally THZ531 was synergistic with both PARP inhibitors and DNA damaging agents in ovarian and breast cancer cell lines. These data highlight cancer indications and combinations that may be particularly amenable to treatment with CDK12/13 inhibitors. While the pharmacokinetic properties of THZ531 preclude adequate target engagement in tumor tissue at tolerated doses in mouse model systems, our ongoing medicinal chemistry program is progressing to identify and optimize CDK12/13 inhibitors suitable for clinical evaluation.

Citation Format: Michael Bradley, Jason Marineau, Yoon Choi, Kristin Hamman, Goran Malojcic, David Orlando, Yixuan Ren, Nan Ke, Shanhu Hu, Eric Olson, Christian Fritz, Christopher Roberts. Targeting the transcriptional kinases CDK12 and CDK13 in breast and ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1143. doi:10.1158/1538-7445.AM2017-1143