Protocol to isolate nuclei from Chlamydomonas reinhardtii for ATAC sequencing

The isolation of sufficient amounts of intact nuclei is essential to obtain high-resolution maps of chromatin accessibility via assay for transposase-accessible chromatin using sequencing (ATAC-seq). Here, we present a protocol for tag-free isolation of nuclei from both cell walled and cell wall-deficient strains of the green model alga Chlamydomonas reinhardtii at a suitable quality for ATAC-seq. We describe steps for nuclei isolation, quantification, and downstream ATAC-seq. This protocol is optimized to shorten the time of isolation and quantification of nuclei.

Sporadic bovine encephalopathy caused by Chlamydia pecorum secondary to bovine viral diarrhoea virus infection in calves in South Australia

BACKGROUND

Despite bovine viral diarrhoea virus and Chlamydia pecorum being important endemic diseases of cattle, there are limited reports of theirco-occurrence.

CASE REPORT

Several 12-18-week-old, weaned Hereford calves presented with ill-thriftiness and neurological signs on a mixed cattle and sheep farm in South Australia in July 2021. Immune suppression resulting from transient infection with bovine viral diarrhoea virus (BVDV) is implicated in predisposing to infection with Chlamydia pecorum, the causative agent of sporadic bovine encephalopathy (SBE). Chlamydia spp. are difficult to culture in vitro or definitively identify based on current standard molecular based tests. In this case, diagnosis was confirmed by immunohistochemistry.

CONCLUSION

To the authors' knowledge, this case report is the first to document BVDV transient infection occurring in conjunction with SBE. Given the current high prevalence of BVDV on Australian farms, such co-infections may have significant future clinical relevance. This case also highlights the need for appropriate tests, such as immunohistochemistry to demonstrate the causative organism in histological lesions and thus reduce the occurrence of false negative diagnosis.

Prospects and perspectives: inferring physiological and regulatory targets for CAM from molecular and modelling approaches

BACKGROUND AND SCOPE

This review summarizes recent advances in our understanding of Crassulacean Acid Metabolism (CAM) by integrating evolutionary, ecological, physiological, metabolic and molecular perspectives. A number of key control loops which moderate the expression of CAM phases, and their metabolic and molecular control, are explored. These include nocturnal stomatal opening, activation of phosphoenolpyruvate carboxylase by a specific protein kinase, interactions with circadian clock control, as well as daytime decarboxylation and activation of Rubisco. The vacuolar storage and release of malic acid and the interplay between the supply and demand for carbohydrate reserves are also key metabolic control points.

FUTURE OPPORTUNITIES

We identify open questions and opportunities, with experimentation informed by top-down molecular modelling approaches allied with bottom-up mechanistic modelling systems. For example, mining transcriptomic datasets using high-speed systems approaches will help to identify targets for future genetic manipulation experiments to define the regulation of CAM (whether circadian or metabolic control). We emphasize that inferences arising from computational approaches or advanced nuclear sequencing techniques can identify potential genes and transcription factors as regulatory targets. However, these outputs then require systematic evaluation, using genetic manipulation in key model organisms over a developmental progression, combining gene silencing and metabolic flux analysis and modelling to define functionality across the CAM day-night cycle. From an evolutionary perspective, the origins and function of CAM succulents and responses to water deficits are set against the mesophyll and hydraulic limitations imposed by cell and tissue succulence in contrasting morphological lineages. We highlight the interplay between traits across shoots (3D vein density, mesophyll conductance and cell shrinkage) and roots (xylem embolism and segmentation). Thus, molecular, biophysical and biochemical processes help to curtail water losses and exploit rapid rehydration during restorative rain events. In the face of a changing climate, we hope such approaches will stimulate opportunities for future research.

Epiphytic CAM bromeliads indicate vulnerability of tropical forest communities to climate change

BACKGROUND AND SCOPE

Vascular epiphytes have a variety of mechanisms to trap and retain water, including crassulacean acid metabolism (CAM). Niche segregation was investigated for epiphytic bromeliads on the tropical Caribbean island of Trinidad, where habitats range from lowland deciduous forests to high-rainfall montane tropical forests, ~1000 m in elevation.

METHODS

Four tank-impounding bromeliad epiphytes in the genus Aechmea (Ae. aquilega, Ae. fendleri, Ae. nudicaulis and Ae. dichlamydea) with CAM were mapped across their distinct geographical and elevational zonations in northern Trinidad and Tobago. Species distribution modelling was used to determine environmental limitations for each species. Anatomical and physiological measurements included leaf succulence traits, gas exchange and CAM activity; hydraulic conductance and vulnerability; stomatal sensitivity and quantum yield responses to nocturnal temperature and long-term water deficits.

KEY RESULTS

A total of 2876 field observations identified the transitions between the lowland Ae. aquilega and montane Ae. fendleri, occurring >500 m a.s.l. at the drier western end of the Northern Mountain Range and at progressively lower elevations towards the wetter, eastern region. Anatomical and physiological sensitivities of gas exchange, CAM activity and water use, and responses to elevated nocturnal temperatures and drought, were markedly different for Ae. fendleri compared with Ae. aquilega or the ubiquitous Ae. nudicaulis.

CONCLUSIONS

The species distribution model highlighted the susceptibility of Ae. fendleri to a changing climate. For each species, physiological and anatomical traits were tailored to environmental tolerances, consistent with specialist or generalist niche preferences. Using Intergovernmental Panel on Climate Change scenarios, we predict that rapid rainfall and temperature changes will lead to the loss of Ae. fendleri and associated lower (and upper) montane forest communities from Trinidad, seriously impacting both biodiversity and critical ecosystem functions here and in other tropical island habitats. Epiphytic bromeliads act as markers for threatened communities, and their physiological tolerances represent key indicators of climate change impacts.

Bedside open tracheostomy in COVID-19 patients - a safe and swift approach

BACKGROUND

Tracheostomy can be performed as an open surgical procedure, percutaneous, or hybrid and forms an important step in the management of patients infected with coronavirus disease 2019 (COVID-19) requiring weaning from mechanical ventilation. The purpose of this article is to share our experience to performing bedside surgical tracheostomy in COVID-19 patients in a safe and effective manner, whilst minimising the risk of viral transmission, to optimise patient outcomes and reduce risk to healthcare professionals.

MATERIAL AND METHODS

As recommended by ENT UK, we prospectively established a COVID Airway Team within the ENT department at Birmingham Heartlands Hospital, consisting of four head and neck consultant surgeons to perform either open-bedside, open-theatre or percutaneous tracheostomy in COVID-19 patients. A specific stepwise method for bedside open surgical tracheostomy was based on ENT UK and British Laryngological Society recommendations.

RESULTS

Thirty patients underwent tracheostomy during the study period (14 bedside-open, 5 open-theatre, 11 percutaneous). Mean duration of mechanical intubation prior to bedside-open tracheostomy was 14.5 days. The average time for open-bedside tracheostomy was 9 minutes compared to 31 minutes for open-theatre. There were no significant tracheostomy related complications with bedside-open tracheostomy. No healthcare professional involved reported acute COVID-19 infection.

CONCLUSIONS

We describe our effective, safe and swift approach to bedside open tracheostomy during the COVID-19 pandemic. Our experience demonstrated a short mean procedural time, with no tracheostomy-related complications and no reported viral transmission amongst the healthcare members involved.

The Other Mechanisms by Which the Rht Genes Improve the Harvest Index of Wheat

Uncovering the mechanism that underlies the relationship between crop height and grain yield would potentially inform the strategies for improving wheat with optimal height. The aim of the research reported here was to identify the attributes able to produce wheat yield increases in Rht genotypes without further straw-shortening. Attention was given to examination in a controlled environment the question of the mechanistic foundation that determined the relationship between wheat height and yield in lines (Rht-B1b, Rht-D1b, Rht-B1c, Rht-D1c) compared to wild types in Mercia background. In addition to height reduction, this research revealed three other mechanisms by which the Rht genes may also improve the Harvest Index (HI) of wheat: (i) low Specific Leaf Area (SLA), (ii) increased Mean Residence Time (MRT) of Nitrogen (N), and (iii) increased grain number on spike.

POS0512 ANTI-CITRULLINATED PROTEIN ANTIBODY SEROSTATUS DETERMINES 2-YEAR RETENTION OF IV AND SC ABATACEPT IN PATIENTS WITH RA IN A REAL-WORLD SETTING

Background

A treat-to-target approach for RA management is recommended.1,2 However, up to half of patients discontinue DMARD treatment within 18 months.2 Predictive biomarkers, such as anti-citrullinated protein antibodies (ACPAs) and RF, may be useful to stratify patients to the most appropriate treatment. ACTION (AbataCepT In rOutiNe clinical practice; NCT02109666) and ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) were 2-year, international, observational, prospective, multicenter studies of IV and SC abatacept, respectively, for the treatment of RA in routine clinical practice.3,4 Higher retention has been previously reported in patients with double ACPA/RF seropositive RA compared with double ACPA/RF seronegative RA.3,4

Objectives

To assess the independent effect of ACPA or RF single seropositivity on abatacept retention in patients with RA receiving abatacept in a post hoc analysis of ACTION and ASCORE.

Methods

This post hoc analysis included patients aged ≥ 18 years, with active moderate-to-severe RA (ACR/EULAR 2010 criteria) who initiated IV (body weight–adjusted dosing) or SC (125 mg once weekly) abatacept.3,4 Patients were stratified by baseline ACPA/RF status: ACPA+/RF− (ACPA+ only), ACPA/RF double positive (+/+), ACPA−/RF+ (RF+ only), and ACPA/RF double negative (−/−). Abatacept retention rate at 2 years was estimated by Kaplan–Meier (KM) analysis.

Results

Patients with ACPA/RF serostatus data from the ACTION and ASCORE studies (N = 1679 and N = 1748, respectively) were evaluated. Baseline demographic and disease characteristics were similar across studies and serostatus groups (Table 1). In patients with ACPA+ only RA, abatacept retention rates were similar to the +/+ group and greater than the RF+ only and −/− groups (Figure 1). In ASCORE (Figure 1A), retention rates were significantly higher in ACPA+ only and +/+ groups when compared with the −/− group. In contrast, retention rates for patients with RF+ only RA were not significantly different vs −/− patients. Results were similar in ACTION, although the higher retention in the ACPA+ group did not reach statistical significance (Figure 1B).

Table 1.

Baseline demographics and disease characteristics by ACPA/RF status for the ASCORE and ACTION studies

ASCORE+/+RF+ onlyACPA+ only−/−(n = 1079)(n = 142)(n = 184)(n = 343)Age, years57.1 (12.8)58.2 (11.8)57.4 (13.5)57.8 (13.9)DAS28 (CRP)4.7 (1.2)4.6 (1.1)4.4 (1.0)4.8 (1.2)CDAI26.6 (12.5)25.8 (12.0)23.6 (10.9)28.2 (13.2)SDAI28.1 (13.0)27.2 (12.4)24.4 (10.8)29.7 (13.9)ACTION+/+RF+ onlyACPA+ only−/−(n = 1028)(n = 161)(n = 98)(n = 392)Age, years58.2 (12.0)58.4 (13.4)58.5 (14.0)57.0 (13.3)DAS28 (CRP)4.9 (1.1)5.0 (1.1)4.9 (1.0)5.0 (1.1)CDAI28.7 (12.2)29.2 (12.4)28.7 (11.5)30.1 (12.9)SDAI30.4 (13.1)31.2 (13.4)29.8 (11.5)31.7 (13.4)

Data are mean (SD). Patients with missing data for baseline ACPA/RF status are excluded.

Conclusion

In this post hoc analysis of the real-world ACTION and ASCORE studies, ACPA positivity was associated with an increased likelihood of retention over 2 years. Patients with ACPA+ only RA were equally as likely to be retained on abatacept as patients with ACPA/RF double positivity. In contrast, patients with RF+ only RA were less likely to be retained on abatacept over 2 years. These findings suggest that ACPA positivity played a more important role than RF positivity in abatacept retention. The higher retention seen in patients with ACPA+ only vs RF+ only disease demonstrates the key role of ACPA in RA and supports the importance of precision medicine in treating patients.

References

[1]Fraenkel L, et al. Arthritis Care Res (Hoboken) 2021;73:924–39.

[2]Smolen JS, et al. Ann Rheum Dis 2020;79:685–99.

[3]Alten R, et al. Clin Rheumatol 2019;38:1413–24.

[4]Alten R, et al. Ann Rheum Dis 2021;80(suppl 1):OP0180.

Acknowledgements

This study was sponsored by Bristol Myers Squibb. Medical writing and editorial assistance was provided by Fiona Boswell, PhD, of Caudex, and was funded by Bristol Myers Squibb. Study management provided by Syneos (CRO).

Disclosure of Interests

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Paid instructor for: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Consultant of: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Grant/research support from: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Grant/research support from: AbbVie, Amgen, Bristol Myers Squibb, Eli Lilly, Galapagos, Janssen, MSD, Pfizer, Sean Connolly Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Galapagos, Gilead, Pfizer, Grant/research support from: Gilead, Pfizer, UCB, Peter Peichl Speakers bureau: GlaxoSmithKline, Janssen, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, GlaxoSmithKline, Janssen, Novartis, Pfizer, Sanofi, UCB, Yusuf Patel: None declared, Sara Marsal Speakers bureau: Bristol Myers Squibb, Lilly, MSD, Novartis - Sandoz, Pfizer, Roche, Consultant of: AbbVie, Galapagos, Pfizer, Sanofi; IMIDomics (executive role), Grant/research support from: AbbVie, Bristol Myers Squibb, Galapagos, Janssen, Lilly, MSD, Novartis - Sandoz, Pfizer, Roche, Sanofi, UCB, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius-Kabi, Galapagos, Janssen, Lilly, MSD, Novartis, Pfizer, Roche, Sandoz, UCB, Consultant of: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Galapagos, Janssen, Lilly, MSD, Novartis, Pfizer, Sandoz, UCB, Hedley Griffiths Consultant of: Amgen, Raimón Sanmartí Speakers bureau: AbbVie, Bristol Myers Squibb, Lilly, MSD, Pfizer, Roche, Sanofi, Grant/research support from: AbbVie, Bristol Myers Squibb, MSD, Pfizer, Roche, Bettina Bannert Speakers bureau: Novartis Pharma Schweiz AG, Yedid Elbez Consultant of: Bristol Myers Squibb, Employee of: Signifience, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb.

POS0107 ACPA POSITIVITY DETERMINES REMISSION IN PATIENTS WITH RA TREATED WITH IV AND SC ABATACEPT: A POST HOC ANALYSIS OF THE REAL-WORLD OBSERVATIONAL ACTION AND ASCORE STUDIES

Background

The goal of treatment for RA is achieving low disease activity and/or remission1,2; however, disease course and management can be complicated by additional factors that may be influenced by serostatus. Anti-citrullinated protein antibodies (ACPAs) and RF contribute to a more severe RA disease pattern3 and may be useful in predicting response to treatment.4 ACTION (AbataCepT In rOutiNe clinical practice; NCT02109666) and ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) were 2-year, international, observational, prospective, multicenter studies of IV and SC abatacept, respectively, for the treatment of RA in routine clinical practice.4,5 Previous analyses have shown that ACPA/RF double-positive serostatus was associated with better treatment outcomes compared with ACPA/RF double-negative serostatus.4–6

Objectives

To assess the independent effect of ACPA or RF single seropositivity among patients with RA on achieving remission after treatment with abatacept for 2 years, and to compare outcomes among patients with single versus double serostatus.

Methods

This post hoc analysis included patients from ACTION and ASCORE who initiated IV (body weight–adjusted dosing) or SC abatacept (125 mg once weekly), respectively. Patients were stratified by baseline ACPA/RF status: ACPA+/RF− (ACPA+ only), ACPA/RF double positive (+/+), ACPA−/RF+ (RF+ only), and ACPA/RF double negative (−/−). DAS28 (CRP) and CDAI remission rates (defined as < 2.6 and 0–2.8, respectively) at 2 years for patients who were ACPA+ or RF+ only at baseline were assessed and compared with those who were +/+ and −/−. Patients with missing baseline ACPA/RF status were excluded. Last observation carried forward efficacy analyses were used to impute missing values.

Results

This analysis included 1679 patients from ACTION (ACPA+ only, n = 98; +/+, n = 1028; RF+ only, n = 161; and −/−, n = 392) and 1748 patients from ASCORE (ACPA+ only, n = 184; +/+, n = 1079; RF+ only, n = 142; and −/−, n = 343). Across studies and serogroups, baseline demographics and disease characteristics were similar (data not shown). In both ACTION and ASCORE, a higher proportion of patients who were only ACPA+ achieved DAS28 (CRP) and CDAI remission at 2 years compared with patients who were only RF+ (Figure 1). Additionally, a similar proportion of patients who were only ACPA+ achieved DAS28 (CRP) and CDAI remission at 2 years compared with patients who were +/+. In contrast, a lower proportion of patients who were only RF+ achieved DAS28 (CRP) and CDAI remission at 2 years compared with patients who were +/+.

Conclusion

In this post hoc analysis of real-world data from ACTION and ASCORE, ACPA positivity was associated with an increased likelihood of achieving DAS28 (CRP) and CDAI remission at 2 years. Patients who were ACPA+ only were as likely to achieve remission as +/+ patients, suggesting that RF serostatus had less influence than ACPA serostatus on remission status at 2 years. In line with this, patients who were RF+ only were less likely to achieve remission at 2 years. This is the first large, real-world study to show that ACPA positivity plays a more important role than RF positivity in achieving remission whilst on abatacept. These results highlight the importance of assessing baseline ACPA status when considering treatment options for patients with RA.

References

[1]Smolen JS, et al. Ann Rheum Dis 2020;79:685–99.

[2]Fraenkel L, et al. Arthritis Care Res (Hoboken) 2021;73:924–39.

[3]Katchamart, W, et al. Rheumatol Int 2015;35:1693–9.

[4]Alten R, et al. Ann Rheum Dis 2021;80(suppl 1):OP0180.

[5]Alten R, et al. Clin Rheumatol 2019;38:1413–24.

[6]Alten R, et al. RMD Open 2017;3:e000345.

Acknowledgements

This study was sponsored by Bristol Myers Squibb. Medical writing and editorial assistance was provided by Rachel Rankin, PhD, of Caudex, and was funded by Bristol Myers Squibb. Study management provided by Syneos (CRO).

Disclosure of Interests

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Paid instructor for: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Consultant of: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Grant/research support from: AbbVie, Bristol Myers Squibb, Celltrion, Galapagos, Gilead, Janssen, Lilly, Novartis, Pfizer, Roche, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Eli Lilly, Janssen, Pfizer, Grant/research support from: AbbVie, Amgen, Bristol Myers Squibb, Eli Lilly, Galapagos, Janssen, MSD, Pfizer, Sean Connolly Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Galapagos, Gilead, Pfizer, Grant/research support from: Gilead, Pfizer, UCB, Peter Peichl Speakers bureau: Janssen, GlaxoSmithKline, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, GlaxoSmithKline, Janssen, Novartis, Pfizer, Sanofi, UCB, Yusuf Patel: None declared, Sara Marsal Speakers bureau: Bristol Myers Squibb, Lilly, MSD, Novartis - Sandoz, Pfizer, Roche, Consultant of: AbbVie, Galapagos, Pfizer, Sanofi; IMIDomics (executive role), Grant/research support from: AbbVie, Bristol Myers Squibb, Galapagos, Janssen, Lilly, MSD, Novartis - Sandoz, Pfizer, Roche, Sanofi, UCB, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius-Kabi, Galapagos, Janssen, Lilly, MSD, Novartis, Pfizer, Roche, Sandoz, UCB, Consultant of: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Galapagos, Janssen, Lilly, MSD, Novartis, Pfizer, Sandoz, UCB, Hedley Griffiths Consultant of: Amgen, Raimón Sanmartí Speakers bureau: AbbVie, Bristol Myers Squibb, Lilly, MSD, Pfizer, Roche, Sanofi, Grant/research support from: AbbVie, Bristol Myers Squibb, MSD, Pfizer, Roche, Bettina Bannert: None declared, Yedid Elbez Consultant of: Bristol Myers Squibb, Employee of: Signifience, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb

POS0691 EMULATING A TARGET TRIAL OF ADALIMUMAB VERSUS TOFACITINIB IN PATIENTS WITH RHEUMATOID ARTHRITIS: A COMPARATIVE EFFECTIVENESS ANALYSIS USING THE OPAL REAL-WORLD DATASET

Background

There is increasing recognition of the complementary role for real-world evidence (RWE) in health care and regulatory decision-making (1). However, careful analysis is required when drugs are compared using observational data to account for differences between treatment groups. Electronic medical records (EMR) are an important source of real-world data (RWD), but outcomes are often recorded incompletely.

We emulated a target trial of adalimumab (ADA) versus tofacitinib (TOF) in patients with rheumatoid arthritis (RA) using the OPAL dataset to illustrate the application of methodologies to address the challenges of non-random treatment assignment and incomplete data. The OPAL dataset is derived from EMR of 112 community-based rheumatologists around Australia, where practitioners have discretion to prescribe whichever b/tsDMARD they consider most clinically appropriate.

Objectives

To estimate the average treatment effect (ATE) of TOF compared to ADA at 3 and 9 months, defined as the difference in mean disease activity score (DAS28CRP), in patients with RA who are new users of a b/tsDMARD. This is equivalent to aiming to estimate the intention-to-treat effect in a randomised controlled trial.

Methods

OPAL patients diagnosed with RA were included if they initiated ADA or TOF between 1 October 2015 and 1 April 2021, were new b/tsDMARD users (no prior recorded b/tsDMARD, at least 6 months of prior csDMARD treatment), and had at least 1 component of DAS28CRP recorded at baseline or during follow-up. Data were also extracted on baseline characteristics. Baseline characteristics were DAS28CRP, patient demographics, regional location, disease duration, prescriber characteristics (including gender, experience), prior recorded comorbidities, and prior and concomitant treatment with csDMARDs and oral corticosteroids.

We used random forest multiple imputation to impute missing baseline and follow-up DAS28CRP components (2). Stable balancing weights (SBW) were then used to balance the treatment groups in terms of their baseline characteristics, including DAS28CRP (3). For each imputed dataset, the ATE at 3 months was estimated as the difference between the mean outcome in the two treatment groups after balancing (i.e. weighting) the sample, and then these estimates were averaged across the 10 imputed datasets. The ATE at 9 months was estimated similarly. The whole procedure was subsequently performed in 1000 bootstrap samples to estimate a 95% confidence interval (CI) for the ATEs using the percentile method (4).

Results

842 patients were identified including n=569 treated with ADA and n=273 treated with TOF. After applying the SBW, the maximum difference between the mean of each baseline characteristic in the ADA and TOF groups was less than 0.03% of the corresponding standard deviation in the whole sample, indicating reasonable balance was achieved in this complex dataset. After weighting, mean DAS28CRP reduced from 5.3 at baseline (both ADA and TOF groups) to 2.6 and 2.3 at 3 and 9 months for ADA, and 2.4 and 2.3 at 3 and 9 months for TOF.

The estimated ATE was -0.22 (95% CI -0.36, -0.03; p=0.02) at 3 months, indicating a modest but significant reduction in disease activity for patients on TOF. The estimated ATE was -0.03 (95% CI -0.19, 0.1; p=0.56) at 9 months, indicating no difference between groups.

Conclusion

DAS28CRP was significantly lower at 3 months for patients treated with TOF compared to ADA. However, 3 months of treatment with either drug led to substantive average reductions in mean DAS28CRP, consistent with remission. There was no difference between drugs at 9 months. Future work will estimate a per-protocol effect.

References

[1]Arlett et al. Clin Pharmacol Ther 2022;111(1):21–3.

[2]van Buuren and Groothuis-Oudshoorn J Stat Softw 201145(3):1–67

[3]Zubizarreta J Am Stat Assoc 2015;110(511):910–22

[4]Bartlett and Hughes Stat Methods Med Res 2020;29(12):3533–46

Acknowledgements

The authors acknowledge the members of OPAL Rheumatology Ltd and their patients for providing clinical data for this study, and Software4Specialists Pty Ltd for providing the Audit4 platform.

Disclosure of Interests

Claire Deakin: None declared, Bianca De Stavola: None declared, Geoff Littlejohn Consultant of: Abbvie, Janssen, Bristol Myers Squibb, Gilead, Eli Lilly, and MSD, Hedley Griffiths Consultant of: AbbVie and Eli Lilly, Sabina Ciciriello: None declared, Peter Youssef Speakers bureau: AbbVie, Novartis, Eli Lilly, David Mathers: None declared, Paul Bird Speakers bureau: Abbvie, Janssen, Bristol Myers Squibb, Pfizer, Novartis, Gilead, Eli Lilly, Consultant of: Abbvie, Janssen, Bristol Myers Squibb, Pfizer, Novartis, Gilead, Eli Lilly, Imaging consulting for Synarc and Boston Imaging Core Lab., Tegan Smith: None declared, Catherine OSullivan: None declared, Tim Freeman: None declared, Dana Segelov: None declared, David Hoffman: None declared, Shaun Seaman: None declared

GWAS identifies genetic loci underlying nitrogen responsiveness in the climate resilient C4 model Setaria italica (L.)

INTRODUCTION

N responsiveness is the capacity to perceive and induce morpho-physiological adaptation to external and internal Nitrogen (N). Crop productivity is propelled by N fertilizer and requires the breeding/selection of cultivars with intrinsically high N responsiveness. This trait has many advantages in being more meaningful in commercial/environmental context, facilitating in-season N management and not being inversely correlated with N availability over processes regulating NUE. Current lack of its understanding at the physio-genetic basis is an impediment to select for cultivars with a predictably high N response.

OBJECTIVES

To dissect physio-genetic basis of N responsiveness in 142 diverse population of foxtail millet, Setaria italica (L.) by employing contrasting N fertilizer nutrition regimes.

METHODS

We phenotyped S. italica accessions for major yield related traits under low (N10, N25) and optimal (N100) growth conditions and genotyped them to subsequently perform a genome-wide association study to identify genetic loci associated with nitrogen responsiveness trait. Groups of accessions showing contrasting trait performance and allelic forms of specific linked genetic loci (showing haplotypes) were further accessed for N dependent transcript abundances of their proximal genes.

RESULTS

Our study show that N dependent yield rise in S. italica is driven by grain number whose responsiveness to N availability is genetically underlined. We identify 22 unique SNP loci strongly associated with this trait out of which six exhibit haplotypes and consistent allelic variation between lines with contrasting N dependent grain number response and panicle architectures. Furthermore, differential transcript abundances of specific genes proximally linked to these SNPs in same lines is indicative of their N dependence in a genotype specific manner.

CONCLUSION

The study demonstrates the value/ potential of N responsiveness as a selection trait and identifies key genetic components underlying the trait in S. italica. This has major implications for improving crop N sustainability and food security.

Stable isotope signals provide seasonal climatic markers for moss functional groups

Living moss biomass and archival peat deposits represent key indicators of present and past climatic conditions, but prediction of future climatic impacts requires appropriate marker species to be characterized under a range of contemporary conditions. Stable isotope signals in high latitude moss deposits offer potential climatic proxies. Seasonal changes in δ13C and δ18O of organic material (cellulose) in representative functional groups, and associated photosynthetic activity (as chlorophyll fluorescence) have been compared across East Anglia, UK, as a function of tissue water content. Representative species from contrasting acid bog, heathland, and fen woodland habitats were selected for monthly sampling of recent growth tissues between spring 2017 and autumn 2018, with isotopic signals in purified cellulose compared with tissue water, precipitation, and nearby groundwater signals. Sphagnum and Polytrichum groups, which tend to dominate peat formation, provided contrasting and complementary indicators of seasonal variations in carbon assimilation. Cellulose δ18O signals from Sphagnum spp. demonstrate seasonal variations in source precipitation inputs; carbon isotope signals in Polytrichum spp. indicate evaporative demand and photosynthetic limitation.

Orchestral manoeuvres in the light: crosstalk needed for regulation of the Chlamydomonas carbon concentration mechanism

The inducible carbon concentration mechanism (CCM) in Chlamydomonas reinhardtii has been well defined from a molecular and ultrastructural perspective. Inorganic carbon transport proteins, and strategically located carbonic anhydrases deliver CO2 within the chloroplast pyrenoid matrix where Rubisco is packaged. However, there is little understanding of the fundamental signalling and sensing processes leading to CCM induction. While external CO2 limitation has been believed to be the primary cue, the coupling between energetic supply and inorganic carbon demand through regulatory feedback from light harvesting and photorespiration signals could provide the original CCM trigger. Key questions regarding the integration of these processes are addressed in this review. We consider how the chloroplast functions as a crucible for photosynthesis, importing and integrating nuclear-encoded components from the cytoplasm, and sending retrograde signals to the nucleus to regulate CCM induction. We hypothesize that induction of the CCM is associated with retrograde signals associated with photorespiration and/or light stress. We have also examined the significance of common evolutionary pressures for origins of two co-regulated processes, namely the CCM and photorespiration, in addition to identifying genes of interest involved in transcription, protein folding, and regulatory processes which are needed to fully understand the processes leading to CCM induction.

The rare C9 P167S risk variant for age-related macular degeneration increases polymerization of the terminal component of the complement cascade

Age-related macular degeneration (AMD) is a complex neurodegenerative eye disease with behavioral and genetic etiology and is the leading cause of irreversible vision loss among elderly Caucasians. Functionally significant genetic variants in the alternative pathway of complement have been strongly linked to disease. More recently, a rare variant in the terminal pathway of complement has been associated with increased risk, Complement component 9 (C9) P167S. To assess the functional consequence of this variant, C9 levels were measured in two independent cohorts of AMD patients. In both cohorts, it was demonstrated that the P167S variant was associated with low C9 plasma levels. Further analysis showed that patients with advanced AMD had elevated sC5b-9 compared to those with non-advanced AMD, although this was not associated with the P167S polymorphism. Electron microscopy of membrane attack complexes (MACs) generated using recombinantly produced wild type or P167S C9 demonstrated identical MAC ring structures. In functional assays, the P167S variant displayed a higher propensity to polymerize and a small increase in its ability to induce hemolysis of sheep erythrocytes when added to C9-depleted serum. The demonstration that this C9 P167S AMD risk polymorphism displays increased polymerization and functional activity provides a rationale for the gene therapy trials of sCD59 to inhibit the terminal pathway of complement in AMD that are underway.

POS0906 PREVALENCE OF SLEEP DISTURBANCE IN PATIENTS WITH ANKYLOSING SPONDYLITIS WITHIN THE AUSTRALIAN CLINICAL SETTING (ASLEEP STUDY): A REAL-WORLD OBSERVATIONAL STUDY USING THE OPAL DATASET

Background:

Sleep disorders are more prevalent in patients with ankylosing spondylitis (AS) compared to the general population. Sleep disturbance in AS, in addition to pain and fatigue, can lead to impaired physical function and reduced quality of life.

Objectives:

The primary objective was to determine the prevalence of sleep disturbance in patients with AS in a real-world Australian cohort using the Insomnia Severity Index (ISI) and Multivariate Apnoea Prediction Index (MAPI). ISI score of ≥ 15 is considered clinical insomnia. MAPI values below 0.05 are suggestive of clinical apnoea.

Methods:

Routinely collected, de-identified clinical data were sourced from the OPAL dataset. Patients aged between 18 and 95 years with a diagnosis of AS and who had completed at least one ISI or MAPI questionnaire between Jan-2019 and Sept-2020 were included. ISI and MAPI questionnaires were emailed to patients using OPAL’s electronic patient reported outcome (ePRO) delivery method or completed in the clinic using a smart device and returned to the patient’s file using a QR code. Disease activity was assessed using BASDAI collected at the same time as the sleep questionnaires. Age, sex and duration of symptoms were used to propensity match patients in the Il-17ai and TNFi group in a 1:2 ratio.

Results:

495 of the 5,323 patients identified with AS completed a questionnaire and were included in the analysis (n=395 TNFi, n=48 Il-17ai (secukinumab), n=52 other therapies). 142 were included in the propensity score matched population (n = 94 TNFi, and n = 48 Il-17ai). In the overall population the mean (SD) age was 48.3 (13.6), 55.4% were males, the mean (SD) BMI was 30.1 (19.6) at the index date and 4.8% reported depression. 51.7% had an optimal disease control (BASDAI <4). The mean (SD) ISI score was 8.6 (6.2). 48.1% reported no clinical significant insomnia, 32.7% reported subthreshold insomnia, 16% reported clinical insomnia (moderate severity) and 3.2% reported clinical insomnia (severe). The mean (SD) MAPI score was 0.4 (0.3). 292 patients (59.0%) had low risk of clinical apnoea, 134 patients (27.1%) had high risk of clinical apnoea and 69 patients 13.9% had not completed the MAPI questionnaire. In the propensity scored matched population, the TNFi and Il-17ai groups had mean (SD) ISI scores of 9.1 (6.6) and 8.9 (5.9) at index, respectively (p = 0.83) and mean (SD) MAPI scores of 0.3 (0.2) and 0.4 (0.3) at index, respectively (p=0.046), however a higher percentage of overweight and obese patients were identified in the Il-17ai treatment group. Ordered logistic regression analysis of the relationship between demographics and ISI in the matched population found that patients with BASDAI ≥4 were seven times more likely to experience greater sleep disturbance (OR 7.29, 95%CI 2.37 to 22.46, p=0.001) than those with BASDAI <4.

Conclusion:

In this real-world AS cohort, poor disease control was associated with sleep disturbance, despite bDMARD therapy. Little difference was observed between TNFi and Il-17ai treatment. Screening for sleep disturbance and fatigue in routine clinical care may provide a more holistic view of the burden of this disease.

Table 1.

Patient characteristics and outcome scores in the propensity score matched population at index.

TNFi (n=94)Il-17ai (n=48)p valueBMI category Underweight2 (2%)1 (2%)0.094 Normal weight33 (35%)8 (17%) Overweight24 (26%)16 (33%) Obese27 (29%)21 (44%) Missing8 (9%)2 (4%)Duration of treatment (months), mean (SD)61.0 (156.7)23.7 (20.1)0.18BASDAI <443 (46%)23 (48%)0.89BASDAI > 416 (17%)8 (17%)Missing35 (37%)17 (35%)ISI score, mean (SD)9.1 (6.6)8.9 (5.9)0.83ISI category (n (%)0.83 No clinically significant insomnia44 (57%)24 (50%) Subthreshold insomnia30 (32%)15 (31%) Clinical insomnia (moderate)15 (16%)8 (17%) Clinical insomnia (severe)5 (5%)1 (2%)MAPI score, mean (SD)0.3 (0.2)0.4 (0.3)0.046MAPI, high apnoea risk Yes17 (18%)16 (33%)0.051 No62 (66%)26 (54%) Missing15 (16%)6 (12%)

Acknowledgements:

The authors acknowledge the members of OPAL Rheumatology Ltd and their patients for providing clinical data for this study, and Software4Specialists Pty Ltd for providing the Audit4 platform. We acknowledge WriteSource Medical Pty Ltd for providing statistical services. Funding for this study was provided by Novartis.

Disclosure of Interests:

Kathleen Tymms: None declared, Belinda Butcher: None declared, Tracey Sletten: None declared, Tegan Smith: None declared, Catherine OSullivan: None declared, Geoff Littlejohn Consultant of: AbbVie, Bristol Myers Squibb, Eli Lilly, Gilead, Novartis, Pfizer, Janssen, Sandoz, Sanofi and Seqirus., Ricky Sadler Employee of: Current employee of Novartis, Rebecca Tronnberg Employee of: Current employee of Novartis, Hedley Griffiths Consultant of: AbbVie, Gilead, Novartis and Lilly.

POS0619 MODELLING OF DISEASE ACTIVITY IN PATIENTS WITH INFLAMMATORY ARTHROPATHIES TREATED WITH ETANERCEPT ORIGINATOR OR BIOSIMILAR AS FIRST-LINE BIOLOGIC IN AN AUSTRALIAN REAL-WORLD DATASET

Background:

The availability of biosimilars as non-proprietary versions of established biologic disease-modifying anti-rheumatic drugs (bDMARDs) is enabling greater access for patients with rheumatic diseases to effective medications at a lower cost. Since April 2017 both the originator and a biosimilar for etanercept (trade names Enbrel and Brenzys, respectively) have been available for use in Australia.

Objectives:

[1]To model effectiveness of etanercept originator or biosimilar in reducing Disease Activity Score 28-joint count C reactive protein (DAS28CRP) in patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA) or ankylosing spondylitis (AS) treated with either drug as first-line bDMARD

[2]To describe persistence on etanercept originator or biosimilar as first-line bDMARD in patients with RA, PsA or AS

Methods:

Clinical data were obtained from the Optimising Patient outcomes in Australian rheumatoLogy (OPAL) dataset, derived from electronic medical records. Eligible patients with RA, PsA or AS who initiated etanercept originator (n=856) or biosimilar (n=477) as first-line bDMARD between 1 April 2017 and 31 December 2020 were identified. Propensity score matching was performed to select patients on originator (n=230) or biosimilar (n=136) with similar characteristics in terms of diagnosis, disease duration, joint count, age, sex and concomitant medications. Data on clinical outcomes were recorded at 3 months after baseline, and then at 6-monthly intervals. Outcomes data that were missing at a recorded visit were imputed.

Effectiveness of the originator, relative to the biosimilar, for reducing DAS28CRP over time was modelled in the matched population using linear mixed models with both random intercepts and slopes to allow for individual heterogeneity, and weighting of individuals by inverse probability of treatment weights to ensure comparability between treatment groups. Time was modelled as a combination of linear, quadratic and cubic continuous variables.

Persistence on the originator or biosimilar was analysed using survival analysis (log-rank test).

Results:

Reduction in DAS28CRP was associated with both time and etanercept originator treatment (Table 1). The conditional R-squared for the model was 0.31. The average predicted DAS28CRP at baseline, 3 months, 6 months, 9 months and 12 months were 4.0 and 4.4, 3.1 and 3.4, 2.6 and 2.8, 2.3 and 2.6, and 2.2 and 2.4 for the originator and biosimilar, respectively, indicating a clinically meaningful effect of time for patients on either drug and an additional modest improvement for patients on the originator.

Median time to 50% of patients stopping treatment was 25.5 months for the originator and 24.1 months for the biosimilar (p=0.53). An adverse event was the reason for discontinuing treatment in 33 patients (14.5%) on the originator and 18 patients (12.9%) on the biosimilar.

Conclusion:

Analysis using a large national real-world dataset showed treatment with either the etanercept originator or the biosimilar was associated with a reduction in DAS28CRP over time, with the originator being associated with a further modest reduction in DAS28CRP that was not clinically significant. Persistence on treatment was not different between the two drugs.

Table 1.

Respondent characteristics.

Fixed EffectEstimate95% Confidence Intervalp-valueTime (linear)0.900.89, 0.911.5e-63Time (quadratic)1.011.00, 1.011.3e-33Time (cubic)1.001.00, 1.007.1e-23Originator0.910.86, 0.960.0013

Acknowledgements:

The authors acknowledge the members of OPAL Rheumatology Ltd and their patients for providing clinical data for this study, and Software4Specialists Pty Ltd for providing the Audit4 platform.

Supported in part by a research grant from Investigator-Initiated Studies Program of Merck & Co Inc, Kenilworth, NJ, USA. The opinions expressed in this paper are those of the authors and do not necessarily represent those of Merck & Co Inc, Kenilworth, NJ, USA.

Disclosure of Interests:

Claire Deakin: None declared, Geoff Littlejohn Consultant of: Over the last 5 years Geoffrey Littlejohn has received educational grants and consulting fees from AbbVie, Bristol Myers Squibb, Eli Lilly, Gilead, Novartis, Pfizer, Janssen, Sandoz, Sanofi and Seqirus., Hedley Griffiths Consultant of: AbbVie, Gilead, Novartis and Lilly., Tegan Smith: None declared, Catherine OSullivan: None declared, Paul Bird Speakers bureau: Eli Lilly, abbvie, pfizer, BMS, UCB, Gilead, Novartis

POS1461-HPR THE DEVELOPMENT OF A NOVEL EPRO DELIVERY SYSTEM TO MEASURE PATIENT QUALITY OF LIFE IN ROUTINE CLINICAL CARE: AN ANALYSIS OF 5 YEARS OF EXPERIENCE

Background:

Registry studies and clinical trials are increasingly incorporating patient reported outcomes (PROs) to measure the full burden of disease and better measure the efficacy and value of medicines; however, the burden of paper-based surveys, time constraints, and privacy concerns impede the widespread use of PROs in routine clinical care.

Objectives:

To develop a simple and secure technological solution to incorporate validated PROs into routine clinical care for patients with rheumatic diseases, and to assess the patient response to functional assessment of chronic illness therapy fatigue (FACIT-F), patient health questionnaire-2 (PHQ-2), and healthcare resource utilization (HCRU) questionnaires delivered using this ePRO method.

Methods:

A novel ePRO questionnaire delivery system was developed by Software4Specialists in partnership with OPAL Rheumatology. Validated PRO questionnaires were sent from the patient’s electronic medical record (Audit4, Software4Specialists) and delivered to the patient’s email address at time intervals specified by the rheumatologist (defaults to quarterly) or completed in the clinic waiting room prior to the consultation using a tablet or the patient’s smart phone (in-practice). Completed questionnaires were encrypted and returned directly to the patient’s Audit4 electronic medical record held on the clinician’s server for review at the next clinical consultation. The link to the PRO questionnaire expired within 28 days if the questionnaire was not completed, and the questionnaires were automatically cancelled if 2 consecutive links expired. This technology was made available to up to 111 rheumatologists located in 42 clinics in 6 states/territories in Australia, and the use of this technology to furnish the clinical consultation was voluntary for clinicians and patients. Deidentified clinical data was extracted from the servers of participating rheumatologists and aggregated across all sites.1 Data collected between April 2016-Dec 2020 was analysed descriptively.

Results:

Between April 2016-Dec 2020, 99,505 FACIT-F, PHQ-2 and HCRU questionnaires have been delivered to 5,784 patients from 39 of 42 contributing clinics (93%). 85% of questionnaires were delivered via email and 15% in-practice. Overall, 85% of patients completed at least one questionnaire, and of all questionnaires sent, 73% were completed. These rates have remained consistent over time. The completion rates were higher when questionnaires were delivered to patients in-practice compared to email (96% vs 69%). Females were more likely to engage with the questionnaires than males (87% vs 81%), and older patients were slightly more likely to complete all questionnaires delivered. 69% of questionnaires sent via email were completed on the day they were delivered and 94% were completed within 7 days. The median (IQR) number of questionnaires completed per patient was 3 (1,7) and the median (IQR) time since the first questionnaire was completed was 13 months (5,26).

Conclusion:

The novel Audit4 ePRO delivery system is an effective tool for incorporating PROs into routine clinical care to capture data directly from the patient on the impact of their condition on their quality of life. The data generated provides a unique opportunity to understand the full burden of disease for patients in the real-world setting and the impact of interventions.

References:

[1]Littlejohn GO, Tymms KE, Smith T, Griffiths HT. Using big data from real-world Australian rheumatology encounters to enhance clinical care and research. Clin Exp Rheum 2020:38(5): 874 -880.

Acknowledgements:

The authors acknowledge the members of OPAL Rheumatology Ltd and their patients for providing clinical data for this study, and Software4Specialists Pty Ltd for providing the Audit4 platform.

Disclosure of Interests:

Kathleen Tymms: None declared, Tegan Smith: None declared, Claire Deakin: None declared, Tim Freeman: None declared, David Hoffman: None declared, Dana Segelov: None declared, Hedley Griffiths Consultant of: AbbVie, Gilead, Novartis and Lilly., Sabina Ciciriello: None declared, Peter Youssef: None declared, David Mathers: None declared, Catherine OSullivan: None declared, Geoff Littlejohn Consultant of: Over the last 5 years Geoffrey Littlejohn has received educational grants and consulting fees from AbbVie, Bristol Myers Squibb, Eli Lilly, Gilead, Novartis, Pfizer, Janssen, Sandoz, Sanofi and Seqirus

Leaf water δ18O reflects water vapour exchange and uptake by C3 and CAM epiphytic bromeliads in Panama

The distributions of CAM and C3 epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (δ13C) signals, and epiphyte water balance was investigated via oxygen isotopes (δ18O) across wet and dry seasons. There were significant seasonal differences in leaf water (δ18Olw), precipitation, stored 'tank' water and water vapour. Values of δ18Olw were evaporatively enriched at low altitude in the dry season for the C3 epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) δ18Olw values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C3 δ18Olw also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C3) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C3 and CAM bromeliads, δ18Olw became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C3 W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative δ18O exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C3 and CAM systems.

POS0223 PATTERNS OF JANUS KINASE INHIBITOR CYCLING FOR THE MANAGEMENT OF RHEUMATOID ARTHRITIS IN REAL-WORLD CLINICAL PRACTICE: AN ANALYSIS OF THE OPAL DATASET

Background:

There are currently eleven biologic and targeted synthetic (b/ts)DMARDs acting via five different modes of action available for the treatment of RA in Australia. The cost of b/tsDMARDs is subsidized by government for patients that have active RA despite six months of combination csDMARD therapy. Once a patient is eligible, the clinician can prescribe the b/tsDMARD they deem to be the most clinically appropriate for the patient. In Oct 2015 the first JAK inhibitor (JAKi) became available in Australia (tofacitinib, TOF), baricitinib (BARI) became available in Sept 2018, and upadacitinib (UPA) in May 2020. Each of these oral tsDMARDs possess different selectivity profiles towards different members of the JAK family (JAK1–3 and Tyk2).

Objectives:

The aim of this analysis was to determine the patterns of JAKi cycling in real-world practice in Australia.

Methods:

Deidentified clinical data were sourced from the OPAL dataset, which is collected in a custom-built electronic medical record during the routine consultation1. Data from patients >18 years with RA who commenced a b/tsDMARD between Jan-2007 and Dec-2020 were included in the analysis. A visual analytics software program was used to display data on medication initiation and cessation dates, and reasons for stopping tsDMARDs, which is recorded in the medical record at the time of the decision.

Results:

At Dec 2020, 28% of the 52,190 patients with RA in the OPAL dataset were prescribed b/tsDMARDs. Of these patients, 3,850 (26.3%) were currently prescribed a JAKi with 51.4% receiving TOF, 29.2% BARI and 19.4% UPA. In 2020, JAKi initiations accounted for 48.8% of all initiations and 30.7% of 1st line initiations; an increase of 6.1% and 3.5% from 2019, respectively. The percentage of patients switching from a first line JAKi to a second line JAKi rather than an agent with another mode of action increased from 33.1% in 2019 to 42.6% in 2020. This is despite 26.2% in 2019 and 45.8% in 2020 of the patients switching to another JAKi citing lack of efficacy as the reason for JAKi discontinuation. In the period between May 2020, when a third JAKi (UPA) become available, and Dec 2020, the majority of patients switching from first line TOF or BARI to another JAKI switched to UPA (69.4% and 83.9%, respectively), whilst 30.6% of first line TOF patients switched to BARI (30.6%), and 16.1% of first line BARI patients switched to TOF in second line. The majority of patients switching from second line TOF or BARI to a third line JAKi switched to UPA (73% and 96%, respectively), with 27% of second line TOF patients switching to BARI and a very low number moving from second line BARI to TOF (4%). JAKi choice after a third line TOF or BARI was almost exclusively UPA (86.2% and 95.5%, respectively).

Conclusion:

There has been significant and sustained uptake of JAKi for the management of RA in Australia and JAKi cycling is increasingly common in routine clinical care. Clinical outcomes and persistence following JAKi cycling requires further investigation.

References:

[1]Littlejohn GO, Tymms KE, Smith T, Griffiths HT. Using big data from real-world Australian rheumatology encounters to enhance clinical care and research. Clin Exp Rheumatol. Sep-Oct 2020;38(5):874-880.

Figure 1.

Patterns of JAKi cycling for the management of rheumatoid arthritis in first, second and third line switching.

Acknowledgements:

The authors acknowledge the members of OPAL Rheumatology Ltd and their patients for providing clinical data for this study, and Software4Specialists Pty Ltd for providing the Audit4 platform

Disclosure of Interests:

Sabina Ciciriello: None declared, Tegan Smith: None declared, Catherine OSullivan: None declared, Kathleen Tymms: None declared, Peter Youssef: None declared, David Mathers: None declared, Claire Deakin: None declared, Hedley Griffiths Consultant of: AbbVie, Gilead, Novartis and Lilly., Geoff Littlejohn Speakers bureau: Over the last 5 years Geoffrey Littlejohn has received educational grants and consulting fees from AbbVie, Bristol Myers Squibb, Eli Lilly, Gilead, Novartis, Pfizer, Janssen, Sandoz, Sanofi and Seqirus.

POS0447 PHYSICAL FUNCTION IN PATIENTS WITH RA, STRATIFIED BY SEROSTATUS AND TREATMENT LINE, FOLLOWING SC ABATACEPT: POST HOC ANALYSIS OF AN OBSERVATIONAL, 2-YEAR STUDY CONDUCTED IN ROUTINE CLINICAL PRACTICE (ASCORE)

Background:

RA is characterised by the production of autoantibodies, including RF and anti-citrullinated protein antibodies (ACPAs).1 Seropositive disease is associated with poorer prognosis in patients with RA,2 and response to different treatments has been shown to vary based on ACPA status.3 ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) was a 2-year, observational, prospective, multicentre study of SC abatacept for the treatment of RA.4

Objectives:

This post hoc analysis of the ASCORE study evaluated patient-reported outcomes, assessed using HAQ-DI, by RF/ACPA serostatus and treatment line over 24 months of treatment with abatacept.

Methods:

Eligible patients, aged ≥18 years, with active moderate-to-severe RA (ACR/EULAR 2010 criteria) who were IV abatacept-naive and initiated SC abatacept 125 mg once weekly, were enrolled into two cohorts: biologic (b)DMARD-naive patients and those with ≥1 prior bDMARD treatment failure. This post hoc analysis assessed mean change from baseline in HAQ-DI score at 6, 12, 18 and 24 months in response to treatment with abatacept stratified by baseline serostatus (RF/ACPA double positive [+/+]; RF/ACPA single positive [+/−; RF+/ACPA– or RF–/ACPA+] or RF/ACPA double negative [–/–]) and by line of therapy (all patients, patients receiving abatacept as a first-line bDMARD or as a ≥ second-line bDMARD [data not shown], and those receiving abatacept following 1 [data not shown] or ≥2 prior bDMARDs). Estimates of mean difference with 95% CIs between patients with different serostatus were calculated using a t-test for all patients and within different lines of therapy.

Results:

Among 2892 eligible patients in ASCORE, 1748 patients with RF/ACPA status available at baseline were included in this analysis (1079 +/+, 326 +/– and 343 –/–). Of these, 791 patients received abatacept as a first-line bDMARD therapy and 957 as a ≥ second-line bDMARD therapy (505 patients had received ≥2 prior bDMARDs). Among all patients, mean change from baseline in HAQ-DI score at 6 months was greater for patients with +/+ RA (mean difference [95% CI]: –0.2 [–0.3, –0.0]; p=0.0068) or +/– RA (mean difference [95% CI]: –0.2 [–0.3, –0.0]; p=0.0315) versus those with –/– RA at baseline (Figure 1). Similarly, mean change (95% CI) in HAQ-DI score at 6 months was greater for patients with +/+ RA versus –/– RA among those receiving abatacept as first-line therapy (–0.2 [–0.4, –0.0]; p=0.0407) or following treatment with ≥2 bDMARDs (–0.3 [–0.5, –0.0]; p=0.0265) (Figure 1). Among patients treated with abatacept following ≥2 prior bDMARDs, mean change in HAQ-DI score was higher among patients with +/– RA versus –/– RA at 18 months (data not shown) and 24 months (Figure 1). No other significant differences were observed by serostatus or line of therapy at any other time points.

Conclusion:

Patients with RA who were RF+/ACPA+ at baseline showed an enhanced initial response to abatacept compared with those who were RF–/ACPA–. Over 24 months of treatment in this real-world setting, abatacept was equally effective as a first- or ≥ second-line therapy.

References:

[1]Scott DL, et al. Lancet 2010;376:1094–1108.

[2]Hecht C, et al. Ann Rheum Dis 2015;74:2151–2156.

[3]Harrold LR, et al. J Rheumatol 2018;45:32–39.

[4]Alten R, et al. Ann Rheum Dis 2019;78(suppl 2):A1639.

Acknowledgements:

Professional medical writing and editorial assistance was provided by Fiona Boswell, PhD, at Caudex and was funded by Bristol Myers Squibb. This study was funded by Bristol Myers Squibb.

Disclosure of Interests:

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Grant/research support from: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, Gilead, GlaxoSmithKline, Janssen, Pfizer, UCB, Rene-Marc Flipo Speakers bureau: AbbVie, Bristol Myers Squibb, Janssen, Lilly, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche-Chugai, Grant/research support from: Amgen, Janssen, Novartis, Pfizer, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius Kabi, Galapagos, Gilead, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Samsung Bioepis, Sanofi, UCB, Consultant of: Galapagos, Gilead, Janssen, Lilly, Merck Sharp & Dohme, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Eli Lilly, Gilead, Merck Serono, Pfizer, Roche, Sanofi, Grant/research support from: Gilead, Pfizer, Roche, UCB, Yusuf Patel: None declared, Sara Marsal Speakers bureau: Bristol Myers Squibb, Celgene, Pfizer, Roche, Sanofi, UCB, Consultant of: AbbVie, Bristol Myers Squibb, Celgene, Galapagos, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Janssen, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Sanofi, UCB, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Roche, Sanofi, Consultant of: AbbVie, Celgene, Celltrion, Eli Lilly, Janssen, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Eli Lilly, Janssen, Merck Sharp & Dohme, Mundipharma, Novartis, Pfizer, Roche, Sanofi, Hedley Griffiths Consultant of: AbbVie, Gilead, Janssen, Novartis, Peter Peichl: None declared, Bettina Bannert: None declared, Adrian Forster: None declared, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Yedid Elbez Consultant of: Bristol Myers Squibb, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Vadim Khaychuk Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb

OP0180 IMPACT OF RF AND ANTI-CITRULLINATED PROTEIN ANTIBODY SEROSTATUS ON 2-YEAR RETENTION OF ABATACEPT IN PATIENTS WITH RA

Background:

Up to 50% of patients with RA discontinue DMARD treatment within 18 months.1 However, up to 20% of patients who fail multiple treatments may have a good treatment response to another therapy.1 Predictive biomarkers, such as RF and anti-citrullinated protein antibodies (ACPAs), may be useful to stratify patients with RA to the most appropriate treatment.1 ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) was a 2-year, observational, prospective, multicentre study of SC abatacept for the treatment of RA in routine clinical practice.2

Objectives:

To determine if RF/ACPA serostatus and treatment line impact abatacept retention in patients with RA in a post hoc analysis of ASCORE.

Methods:

Eligible patients, aged ≥18 years, with active moderate-to-severe RA (ACR/EULAR 2010 criteria) who were IV abatacept-naive and initiated SC abatacept 125 mg once weekly, were enrolled into two cohorts: biologic (b)DMARD-naive patients and those with ≥1 prior bDMARD treatment failure. This post hoc analysis assessed abatacept retention rate at 2 years in a subset of patients with RF/ACPA serostatus data (n=1748) from the ASCORE study (N=2892; as observed). Baseline (BL) serostatus groups examined by treatment line were: RF/ACPA double positive (+/+) RA, RF/ACPA single positive (RF+/ACPA– or RF–/ACPA+) RA (data not shown) and RF/ACPA double negative (–/–) RA. Last observation carried forward (LOCF) analyses were used to assess change from BL and measures of disease remission (DAS28 [CRP] <2.6, CDAI ≤2.8, and SDAI ≤3.3) in patients with +/+ RA versus –/– RA.

Results:

BL demographic and disease characteristics were similar across serostatus groups and treatment lines (Table 1). Mean age was 57.1 and 57.8 years for +/+ RA and –/– RA, respectively. Mean DAS28 (CRP) was 4.7 and 4.8 for +/+ RA and –/– RA, respectively. In patients with +/+ RA, abatacept retention was greater when given as first-line treatment (57% vs 48% when given as ≥ second-line) (Figure 1). Retention was similar in patients with –/– RA regardless of treatment line. After 2 years, mean (SE) change from BL (LOCF) in DAS28 (CRP) was –1.41 (0.06) and –0.97 (0.09) for patients with +/+ and –/– RA, respectively. For patients with +/+ RA, mean (SE) change from BL in DAS28 (CRP) was –1.62 (0.08) for those in whom abatacept was first-line and –1.19 (0.08) for those in whom abatacept was ≥ second-line. For patients with –/– RA, mean (SE) change from BL in DAS28 (CRP) was –1.03 (0.13) for those in whom abatacept was first-line and –0.93 (0.12) for those in whom abatacept was ≥ second-line. Remission rates (LOCF) were significantly (p<0.0001) higher in patients with +/+ RA vs –/– RA respectively: DAS28 (CRP) 38.4% (n=393) versus 19.3% (n=62); CDAI 50.6% (n=513) versus 33.0% (n=107); and SDAI 49.5% (n=497) versus 32.5% (n=102).

Table 1.

BL demographics and disease characteristics by RF/ACPA status

+/+ RA(n=1079)–/– RA(n=343)First-line (n=511)≥ second-line (n=568)First-line(n=140)≥ second-line(n=203)Age57.1 (13.4)57.1 (12.2)59.5 (14.7)56.6 (13.2)DAS28 (CRP)4.7 (1.2)4.7 (1.2)4.8 (1.1)4.8 (1.2)CDAI26.6 (12.5)26.6 (12.4)27.7 (12.5)28.6 (13.8)SDAI28.1 (13.1)28.1 (12.9)29.1 (12.9)30.2 (14.7)

Data are mean (SD). Patients with missing data for BL RF/ACPA status are excluded.

ACPA=anti-citrullinated protein antibody; BL=baseline.

Conclusion:

In this real-world analysis, patients with +/+ RA treated with first-line abatacept had higher retention than patients receiving abatacept as a ≥ second-line therapy. Remission rates on abatacept were higher in patients with +/+ RA versus –/– RA. These results support early treatment with abatacept and highlight the importance of further evaluating precision medicine approaches in RA.

References:

[1]Smolen JS, et al. Ann Rheum Dis 2020;79:685–699.

[2]Alten R, et al. Ann Rheum Dis 2019;78(suppl 2):A1639.

Acknowledgements:

Professional medical writing and editorial assistance was provided by Lindsay Craik at Caudex and was funded by Bristol Myers Squibb. This study was funded by Bristol Myers Squibb.

Disclosure of Interests:

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Grant/research support from: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, Gilead, GlaxoSmithKline, Janssen, Pfizer, UCB, Rene-Marc Flipo Speakers bureau: AbbVie, Bristol Myers Squibb, Janssen, Lilly, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche-Chugai, Grant/research support from: Amgen, Janssen, Novartis, Pfizer, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius Kabi, Galapagos, Gilead, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Samsung Bioepis, Sanofi, UCB, Consultant of: Galapagos, Gilead, Janssen, Lilly, Merck Sharp & Dohme, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Eli Lilly, Gilead, Merck Serono, Pfizer, Roche, Sanofi, Grant/research support from: Gilead, Pfizer, Roche, UCB, Yusuf Patel: None declared, Raimón Sanmartí Speakers bureau: AbbVie, Bristol Myers Squibb, Gebro, Janssen, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Consultant of: AbbVie, Bristol Myers Squibb, Gebro, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Grant/research support from: Bristol Myers Squibb, Merck Sharp & Dohme, Pfizer, Sara Marsal Speakers bureau: Bristol Myers Squibb, Celgene, Pfizer, Roche, Sanofi, UCB, Consultant of: AbbVie, Bristol Myers Squibb, Celgene, Galapagos, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Janssen, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Sanofi, UCB, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Roche, Sanofi, Consultant of: AbbVie, Celgene, Celltrion, Eli Lilly, Janssen, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Eli Lilly, Janssen, Merck Sharp & Dohme, Mundipharma, Novartis, Pfizer, Roche, Sanofi, Hedley Griffiths Consultant of: AbbVie, Gilead, Janssen, Novartis, Peter Peichl: None declared, Bettina Bannert: None declared, Adrian Forster: None declared, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Sean Connolly Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Yedid Elbez Consultant of: Bristol Myers Squibb, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Vadim Khaychuk Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb

POS0599 DISEASE ACTIVITY IN PATIENTS WITH RA BY SEROSTATUS AND TREATMENT LINE, FOLLOWING TREATMENT WITH ABATACEPT: RESULTS FROM AN INTERNATIONAL OBSERVATIONAL STUDY

Background:

RF and anti-citrullinated protein antibodies (ACPAs) are associated with a severe and aggressive disease course in patients with RA.1 Abatacept is a selective co-stimulation modulator for the treatment of RA.2 ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) was a 2-year, observational, prospective, multicentre study of SC abatacept for the treatment of RA in routine clinical practice.3

Objectives:

To determine if serostatus and treatment line impacted disease activity in patients enrolled in the ASCORE study.

Methods:

Eligible patients, aged ≥18 years, with active moderate-to-severe RA (ACR/EULAR 2010 criteria) who were IV abatacept-naive and initiated SC abatacept 125 mg once weekly, were enrolled into two cohorts: biologic (b)DMARD-naive patients and those with ≥1 prior bDMARD treatment failure. This post hoc analysis assessed the mean change in disease activity (CDAI, SDAI and DAS28 [ESR]) from baseline (BL) at 6, 12, 18 and 24 months in response to treatment with abatacept. Patients were stratified by BL serostatus (all patients, RF/ACPA double positive [+/+] RA; RF/ACPA single positive [+/–; RF+/ACPA– or RF–/ACPA+] RA and RF/ACPA double negative [–/–] RA) and by line of therapy (all patients, patients receiving abatacept as a first-line or ≥ second-line therapy and those receiving abatacept following 1 or ≥2 prior bDMARDs). Overall patient data, as well as data for patients who were +/– or those who had 1 or ≥2 previous bDMARDs, are not shown. Estimates of mean difference are from t-test.

Results:

Among 2892 eligible patients in ASCORE, 1748 patients with RF/ACPA status available at BL were included in this analysis (1079 +/+ RA, 326 +/− RA and 343 −/− RA). After 6 months, patients with +/+ RA on first-line abatacept therapy had better improvements in CDAI and SDAI scores from BL than patients on ≥ second-line abatacept therapy (mean difference [95% CI]: –3.4 [–5.6, –1.1]; p=0.0032 and –3.9 [–6.5, –1.3]; p=0.0035, respectively); better improvements in SDAI were also seen after 12 months (mean difference [95% CI]: –3.5 [–6.5, –0.5]; p=0.0207). Changes in CDAI and SDAI scores were comparable after 18 and 24 months. At 6 and 12 months, patients with +/+ RA on first-line therapy had better improvements from BL in DAS28 (ESR) than those on ≥ second-line therapy (mean differences [95% CI]: –0.5 [–0.8, –0.2]; p=0.0002 and –0.4 [–0.7, –0.0]; p=0.0317, respectively); changes were comparable at 18 and 24 months (Figure 1). For patients on ≥ second-line therapy, at 18 months those with +/+ RA had better improvements from BL in DAS28 (ESR) than those with –/– RA (mean difference [95% CI]: –0.7 [–1.2, –0.1]; p=0.0232). For patients not stratified by line of therapy, changes in DAS28 (ESR) were comparable between the +/+ and –/– RA subgroups over time, with the exception of 6 months where patients with –/– RA had better improvements from BL compared with patients with +/+ RA (mean difference [95% CI]: –0.3 [–0.6, –0.0]; p=0.0495).

Conclusion:

In this real-world, post hoc analysis, patients with +/+ RA who received abatacept as a first-line therapy had greater early improvements in disease activity compared with patients who received abatacept as a ≥ second-line therapy. Improvements in disease activity at 24 months were comparable between patients who were +/+ and those who were –/–. Larger studies are needed to further corroborate these findings.

References:

[1]Katchamart W, et al. Rheumatol Int 2015;35:1693–1699.

[2]Malmström V, et al. Nat Rev Immunol 2017;17:60–75.

[3]Alten R, et al. Ann Rheum Dis 2019;78(Suppl 2):A1639.

Acknowledgements:

Professional medical writing and editorial assistance was provided by Rachel Rankin, PhD, at Caudex and was funded by Bristol Myers Squibb. This study was funded by Bristol Myers Squibb.

Disclosure of Interests:

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Grant/research support from: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, Gilead, GlaxoSmithKline, Janssen, Pfizer, UCB, Rene-Marc Flipo Speakers bureau: AbbVie, Bristol Myers Squibb, Janssen, Lilly, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche-Chugai, Grant/research support from: Amgen, Janssen, Novartis, Pfizer, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius Kabi, Galapagos, Gilead, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Samsung Bioepis, Sanofi, UCB, Consultant of: Galapagos, Gilead, Janssen, Lilly, Merck Sharp & Dohme, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Eli Lilly, Gilead, Merck Serono, Pfizer, Roche, Sanofi, Grant/research support from: Gilead, Pfizer, Roche, UCB, Yusuf Patel: None declared, Raimón Sanmartí Speakers bureau: AbbVie, Bristol Myers Squibb, Gebro, Janssen, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Consultant of: AbbVie, Bristol Myers Squibb, Gebro, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Grant/research support from: Bristol Myers Squibb, Merck Sharp & Dohme, Pfizer, Sara Marsal Speakers bureau: Bristol Myers Squibb, Celgene, Pfizer, Roche, Sanofi, UCB, Consultant of: AbbVie, Bristol Myers Squibb, Celgene, Galapagos, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Janssen, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Sanofi, UCB, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Roche, Sanofi, Consultant of: AbbVie, Celgene, Celltrion, Eli Lilly, Janssen, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Eli Lilly, Janssen, Merck Sharp & Dohme, Mundipharma, Novartis, Pfizer, Roche, Sanofi, Hedley Griffiths Consultant of: AbbVie, Gilead, Janssen, Novartis, Peter Peichl: None declared, Bettina Bannert: None declared, Adrian Forster: None declared, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Yedid Elbez Consultant of: Bristol Myers Squibb, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Vadim Khaychuk Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb

AB0207 ANALYSIS OF ABATACEPT TREATMENT RETENTION AND EFFICACY ACCORDING TO DISEASE DURATION AND TREATMENT LINE IN A REAL-WORLD SETTING

Background:

Longer disease duration and greater number of prior DMARDs have been associated with lower treatment efficacy in patients with RA.1 Abatacept is a biologic (b)DMARD for treatment of moderate-to-severe RA and is available in SC formulation, which may offer convenience benefits with efficacy similar to IV administration.2 ASCORE (Abatacept SubCutaneOus in Routine Clinical PracticE; NCT02090556) was a 2-year, observational, prospective, multicentre study of SC abatacept for treatment of RA in routine clinical practice.3

Objectives:

This post hoc analysis was conducted to determine if retention and efficacy of abatacept were impacted by disease duration and/or treatment line.

Methods:

Eligible patients, aged ≥18 years, with active moderate-to-severe RA (ACR/EULAR 2010 criteria) who were IV abatacept-naive and initiated SC abatacept 125 mg once weekly, were enrolled into two cohorts: bDMARD-naive patients and those with ≥1 prior bDMARD treatment failure. This post hoc analysis evaluated abatacept retention using Kaplan-Meier estimates, as well as disease activity scores (DAS28 [ESR]), CDAI and SDAI in patients with disease duration of ≤2, 3–5, 6–10 or >10 years, and in patients taking abatacept as first-line or ≥ second-line treatment.

Results:

Table 1 shows baseline (BL) characteristics. Mean age increased with disease duration; other characteristics were comparable across groups. Retention proportions (95% CIs) at Month 24 were 0.50 (0.4, 0.5), 0.47 (0.4, 0.5), 0.51 (0.5, 0.5) and 0.46 (0.4, 0.5) in the ≤2, 3–5, 6–10 and >10 years’ duration groups, respectively. Proportion of patients (95% CI) with ≤2 years’ duration retaining treatment at Month 24 were 0.51 (0.4, 0.6) among those using abatacept as first-line treatment and 0.44 (0.3, 0.6) among those using abatacept as a ≥ second-line treatment (Figure 1). Proportions (95% CI) at Month 24 were 0.51 (0.5, 0.6), 0.57 (0.5, 0.6) and 0.52 (0.5, 0.6) in first-line patients and 0.43 (0.4, 0.5), 0.48 (0.4, 0.5) and 0.44 (0.4, 0.5) in ≥ second-line patients in the 3–5, 6–10 and >10 years’ duration groups, respectively. Mean (SE) changes from BL in DAS28 (ESR) at Month 24 were –2.12 (0.205), –1.86 (0.151), –2.07 (0.140) and –2.05 (0.115) in the ≤2, 3–5, 6–10 and >10 years’ duration groups, respectively; respective mean (SE) changes in CDAI were –18.74 (1.604), –15.60 (1.099), –18.50 (1.038) and –17.68 (0.850); and respective mean (SE) changes in SDAI were –19.10 (1.873), –15.72 (1.345), –19.54 (1.103) and –17.07 (0.939).

Conclusion:

In this post hoc analysis of the real-world ASCORE trial, patients with RA receiving abatacept in clinical practice as first-line therapy had better retention versus those receiving it as a ≥ second-line treatment, regardless of disease duration at BL. Retention rates were similar across disease duration subgroups. Improvements in disease activity were seen in all duration subgroups, without consistently greater or lesser improvement seen with longer disease duration.

References:

[1]Aletaha D, et al. Ann Rheum Dis 2019;78:1609–1615.

[2]Genovese MC, et al. Arthritis Rheumatol 2011;63:2854–2864.

[3]Alten R, et al. Ann Rheum Dis 2019;78(suppl 2):A1639.

Table 1.

BL characteristics (n=2872)

RA disease duration, years≤2(n=338)3–5(n=655)6–10(n=686)>10(n=1193)Age, years n3386556861193 Mean (SD)55.2 (12.8)55.6 (12.7)56.9 (13.0)59.9 (12.2)Weight, kg n3276296651150 Mean (SD)75.3 (18.1)76.4 (19.0)74.7 (17.4)72.9 (16.0)DAS28 (ESR) n247439441743 Mean (SD)5.2 (1.3)4.9 (1.3)5 (1.2)5.1 (1.3)DAS28 (CRP) n267460467799 Mean (SD)4.7 (1.2)4.6 (1.2)4.7 (1.1)4.7 (1.2)CDAI n269477474805 Mean (SD)26.9 (12.7)25.3 (12.2)26.8 (12.4)26.6 (12.2)SDAI n255448445749 Mean (SD)28.3 (13.3)26.8 (12.9)27.9 (12.6)28.0 (12.7)RF status, n (%) RF+159 (47.0)342 (52.2)345 (50.3)597 (50.0) RF–103 (30.5)152 (23.2)158 (23.0)215 (18.0)Anti-CCP status, n (%) Anti-CCP+165 (48.8)332 (50.7)333 (48.5)516 (43.3) Anti-CCP–89 (26.3)126 (19.2)137 (20.0)175 (14.7)

Patients with missing duration of disease are excluded.

CCP=cyclic citrullinated peptide.

Acknowledgements:

Professional medical writing and editorial assistance was provided by Rob Coover, MPH, at Caudex and was funded by Bristol Myers Squibb. This study was funded by Bristol Myers Squibb.

Disclosure of Interests:

Rieke Alten Speakers bureau: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Consultant of: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Grant/research support from: AbbVie, Bristol Myers Squibb, Gilead, Janssen, Lilly, Pfizer, Xavier Mariette Consultant of: Bristol Myers Squibb, Galapagos, Gilead, GlaxoSmithKline, Janssen, Pfizer, UCB, Rene-Marc Flipo Speakers bureau: AbbVie, Bristol Myers Squibb, Janssen, Lilly, Medac, Merck Sharp & Dohme, Novartis, Pfizer, Roche-Chugai, Grant/research support from: Amgen, Janssen, Novartis, Pfizer, Roberto Caporali Speakers bureau: AbbVie, Amgen, Bristol Myers Squibb, Celltrion, Fresenius Kabi, Galapagos, Gilead, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Samsung Bioepis, Sanofi, UCB, Consultant of: Galapagos, Gilead, Janssen, Lilly, Merck Sharp & Dohme, Maya H Buch Speakers bureau: AbbVie, Consultant of: AbbVie, Eli Lilly, Gilead, Merck Serono, Pfizer, Roche, Sanofi, Grant/research support from: Gilead, Pfizer, Roche, UCB, Yusuf Patel: None declared, Raimón Sanmartí Speakers bureau: AbbVie, Bristol Myers Squibb, Gebro, Janssen, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Consultant of: AbbVie, Bristol Myers Squibb, Gebro, Lilly, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, Grant/research support from: Bristol Myers Squibb, Merck Sharp & Dohme, Pfizer, Sara Marsal Speakers bureau: Bristol Myers Squibb, Celgene, Pfizer, Roche, Sanofi, UCB, Consultant of: AbbVie, Bristol Myers Squibb, Celgene, Galapagos, Merck Sharp & Dohme, Pfizer, Roche, Sanofi, UCB, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Janssen, Merck Sharp & Dohme, Novartis, Pfizer, Roche, Sanofi, UCB, M.T. Nurmohamed Speakers bureau: AbbVie, Bristol Myers Squibb, Eli Lilly, Roche, Sanofi, Consultant of: AbbVie, Celgene, Celltrion, Eli Lilly, Janssen, Grant/research support from: AbbVie, Bristol Myers Squibb, Celgene, Eli Lilly, Janssen, Merck Sharp & Dohme, Mundipharma, Novartis, Pfizer, Roche, Sanofi, Hedley Griffiths Consultant of: AbbVie, Gilead, Janssen, Novartis, Peter Peichl: None declared, Bettina Bannert: None declared, Adrian Forster: None declared, Melanie Chartier Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Yedid Elbez Consultant of: Bristol Myers Squibb, Christiane Rauch Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Vadim Khaychuk Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb, Karissa Lozenski Shareholder of: Bristol Myers Squibb, Employee of: Bristol Myers Squibb

Measurement of ductions and fields of binocular single vision (BSV): orthoptic practice in the UK and Ireland

To evaluate the current clinical practice of quantifying ductions and fields of BSV in the UK and Ireland using an online questionnaire. An anonymous online questionnaire with twenty-one questions was distributed in February 2019 via the British and Irish Orthoptic Society (BIOS) members' newsletter. Objectives were to investigate: methods used, frequency of assessment, limiting factors and opinions of importance. Informed consent was gained to include the responses in the study. The data was analyzed using descriptive statistics and Wilcoxon Signed Ranks Testing. The questionnaire was completed by 105 orthoptists. The methods reported to quantify ductions and fields of BSV respectively were: Goldmann (33% and 34%), Aimark (22 and 23%), Lister (7%), Octopus (5 and 4%), Thomson ocular motility analyzer (2 and 3%), Binocular vision analyzer (2%) and no method reported (30% and 32%). The frequency of measuring ductions and fields of BSV per week (median 1-2) was significantly less than the number of patients seen with limited ocular motility per week (median 6-9). The main reasons for never or rarely measuring ductions or fields of BSV were not enough time, no method available and only on selected patients. Respondents indicated that they would measure ductions and fields of BSV more frequently if a quicker portable method was available (median 3-5 times per week). Most agreed that measurements of ductions and fields of BSV are important (89 and 95% respectively). There is no standardized method of quantitively measuring ductions or fields of BSV, with almost a third of respondents not measuring either. Although most orthoptists agreed these measurements are important, they are infrequently performed. The main factors limiting these assessments are insufficient time and lack of a testing method. If a faster portable device was available, orthoptists would measure ductions and fields of BSV more frequently.

Latitudinal Biogeographic Structuring in the Globally Distributed Moss Ceratodon purpureus

Biogeographic patterns of globally widespread species are expected to reflect regional structure, as well as connectivity caused by occasional long-distance dispersal. We assessed the level and drivers of population structure, connectivity, and timescales of population isolation in one of the most widespread and ruderal plants in the world - the common moss Ceratodon purpureus. We applied phylogenetic, population genetic, and molecular dating analyses to a global (n = 147) sampling data set, using three chloroplast loci and one nuclear locus. The plastid data revealed several distinct and geographically structured lineages, with connectivity patterns associated with worldwide, latitudinal "bands." These imply that connectivity is strongly influenced by global atmospheric circulation patterns, with dispersal and establishment beyond these latitudinal bands less common. Biogeographic patterns were less clear within the nuclear marker, with gene duplication likely hindering the detection of these. Divergence time analyses indicated that the current matrilineal population structure in C. purpureus has developed over the past six million years, with lineages diverging during the late Miocene, Pliocene, and Quaternary. Several colonization events in the Antarctic were apparent, as well as one old and distinct Antarctic clade, possibly isolated on the continent since the Pliocene. As C. purpureus is considered a model organism, the matrilineal biogeographic structure identified here provides a useful framework for future genetic and developmental studies on bryophytes. Our general findings may also be relevant to understanding global environmental influences on the biogeography of other organisms with microscopic propagules (e.g., spores) dispersed by wind.

Rubisco and carbon-concentrating mechanism co-evolution across chlorophyte and streptophyte green algae

Green algae expressing a carbon-concentrating mechanism (CCM) are usually associated with a Rubisco-containing micro-compartment, the pyrenoid. A link between the small subunit (SSU) of Rubisco and pyrenoid formation in Chlamydomonas reinhardtii has previously suggested that specific RbcS residues could explain pyrenoid occurrence in green algae. A phylogeny of RbcS was used to compare the protein sequence and CCM distribution across the green algae and positive selection in RbcS was estimated. For six streptophyte algae, Rubisco catalytic properties, affinity for CO₂ uptake (K_0.5 ), carbon isotope discrimination (δ¹³ C) and pyrenoid morphology were compared. The length of the βA-βB loop in RbcS provided a phylogenetic marker discriminating chlorophyte from streptophyte green algae. Rubisco kinetic properties in streptophyte algae have responded to the extent of inducible CCM activity, as indicated by changes in inorganic carbon uptake affinity, δ¹³ C and pyrenoid ultrastructure between high and low CO₂ conditions for growth. We conclude that the Rubisco catalytic properties found in streptophyte algae have coevolved and reflect the strength of any CCM or degree of pyrenoid leakiness, and limitations to inorganic carbon in the aquatic habitat, whereas Rubisco in extant land plants reflects more recent selective pressures associated with improved diffusive supply of the terrestrial environment.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

THU0209 UPTAKE OF JANUS KINASE INHIBITORS FOR MANAGEMENT OF RHEUMATOID ARTHRITIS IN AUSTRALIA

Background:

JAK inhibitors (JAKi) are oral tsDMARDs with a different mode of action (MOA) to both oral cs- and parenteral bDMARDs. In Australia the cost of b/tsDMARDs for treatment of RA is subsidized if the patient has documented high levels of clinical/laboratory disease activity and has not responded to a pre-specified combination of csDMARDs, including MTX. Once eligible for subsidy the clinician can prescribe the b/tsDMARD deemed most clinically appropriate.

Objectives:

To determine the patterns of use and reasons for initiation and discontinuation of JAKi in real-world rheumatology practice in Australia.

Methods:

Deidentified clinical data were sourced from the OPAL dataset, which is collected in a custom-built electronic medical record at the time of the consultation1by 94 rheumatologists in Australia, representing one third of Australian clinical rheumatologists. Data from patients >18 years with a diagnosis of RA who commenced a b/tsDMARD between Jan-2007 and Sept-2019 were included in the analysis. Tableau®was used to display data on medication initiation and cessation dates, and reasons for starting and stopping b/tsDMARDs, which is recorded at the time of the decision.

Results:

At Sept 2019, there were 45,317 patients with RA in the data set, with 27% prescribed b/tsDMARDs. Of patients currently on treatment at Sept 2019, 53% were receiving a TNFi and 21% a JAKi, with the remainder receiving tocilizumab, abatacept or rituximab. Of patients who commenced their current treatment after JAKi’s become available in Sept 2015, 46% were treated with a TNFi, and 32% were treated with a JAKi. Tofacitinib (TOF) has been the most prescribed b/tsDMARD since Sept 2015 with 22% of all initiations; however, since baricitinib (BARI) became available in Sept 2018, it has taken over as the preferred JAKi with 24% of new initiations compared to 14% for TOF. From Sept 2018-Sept 2019 etanercept and adalimumab were the most commonly prescribed agents in first line, followed by TOF then BARI; however, BARI was the most prescribed agent in lines 2-6+ (figure 1). The main clinician-listed reason for choice of TOF was MOA in 54%, efficacy compared with alternatives in 30%, mode of administration in 7%, efficacy as monotherapy in 7%, and safety in 1%. BARI was chosen for MOA in 35%, efficacy compared with alternatives in 38%, mode of administration in 12%, efficacy as monotherapy in 12%, and safety in 1%. The main reasons for stopping TOF were lack of efficacy (34%), better alternative (25%) and adverse reaction (13%); those for BARI were lack of efficacy (35%) and adverse reaction (25%) which is consistent with the rates observed in the first 12-months of clinical experience with TOF, and better alternative (12%). Patient non-adherence was listed in 1% and 2% of cessations for TOF and BARI, respectively. 45% of patients discontinuing a JAKi in first line switched to a TNFi in second line, and 40% switched to another JAKi, citing lack of efficacy, adverse reaction, and better alternative as the reason for switching.

Figure 1.

Rank of new initiations by line of therapy (Sept 2018-Sept 2019)

Conclusion:

There has been significant and sustained uptake of JAKi for the management of RA in Australia. MOA and perceived efficacy rate much higher than mode of administration for clinicians when selecting a JAKi. Clinical outcomes and persistence following JAKi cycling requires further investigation.

References:

Littlejohn GO, Tymms KE, Smith T, Griffiths HT. Using big data from real-world Australian rheumatology encounters to enhance clinical care and research. Clin Exp Rheum Nov 2019

Disclosure of Interests:

None declared

Model approaches to advance crassulacean acid metabolism system integration

This review summarises recent progress in understanding crassulacean acid metabolism (CAM) systems and the integration of internal and external stimuli to maximise water-use efficiency. Complex CAM traits have been reduced to their minimum and captured as computational models, which can now be refined using recently available data from transgenic manipulations and large-scale omics studies. We identify three key areas in which an appropriate choice of modelling tool could help capture relevant comparative molecular data to address the evolutionary drivers and plasticity of CAM. One focus is to identify the environmental and internal signals that drive inverse stomatal opening at night. Secondly, it is important to identify the regulatory processes required to orchestrate the diel pattern of carbon fluxes within mesophyll layers. Finally, the limitations imposed by contrasting succulent systems and associated hydraulic conductance components should be compared in the context of water-use and evolutionary strategies. While network analysis of transcriptomic data can provide insights via co-expression modules and hubs, alternative forms of computational modelling should be used iteratively to define the physiological significance of key components and informing targeted functional gene manipulation studies. We conclude that the resultant improvements of bottom-up, mechanistic modelling systems can enhance progress towards capturing the physiological controls for phylogenetically diverse CAM systems in the face of the recent surge of information in this omics era.

A Roadmap for Lowering Crop Nitrogen Requirement

Increasing nitrogen fertilizer applications have sustained a growing world population in the 20th century. However, to avoid any further associated environmental damage, new sustainable agronomic practices together with new cultivars must be developed. To date the concept of nitrogen use efficiency (NUE) has been useful in quantifying the processes of nitrogen uptake and utilization, but we propose a shift in focus to consider nitrogen responsiveness as a more appropriate trait to select varieties with lower nitrogen requirements. We provide a roadmap to integrate the regulation of nitrogen uptake and assimilation into varietal selection and crop breeding programs. The overall goal is to reduce nitrogen inputs by farmers growing crops in contrasting cropping systems around the world, while sustaining yields and reducing greenhouse gas (GHG) emissions.

Prion disease and recommended procedures for flexible endoscope reprocessing - a review of policies worldwide and proposal for a simplified approach

Several guidelines recommend specific treatments for endoscopes, procedures of quarantine for endoscopes, or additional treatments for the endoscope washer disinfector (EWD) in suspected or confirmed cases of Creutzfeldt-Jakob disease (CJD) or variant CJD (vCJD) but vary in many details. This study therefore reviewed guidelines on reprocessing flexible endoscopes after use in patients with suspected or confirmed prion disease. In addition, a literature search was performed in Medline on prion, CJD, vCJD, chemical inactivation, transmission healthcare, epidemiology healthcare, concentration tissue human and endoscope. Thus far, no case of CJD or vCJD transmitted by flexible endoscope has been reported. In animals it has been shown that oral uptake of 0.1-5 g of bovine spongiform encephalopathy (BSE)-infected brain homogenate is necessary for transmission. The maximum prion concentration in other tissues (e.g., terminal ileum) is at least 100-fold lower. Automated cleaning of endoscopes alone results in very low total residual protein ≤5.6 mg per duodenoscopes. Recommendations vary between countries, sometimes with additional cleaning, use of alkaline cleaners, no use of cleaners with fixative properties, use of disinfectants without fixative properties or single-use disinfectants. Sodium hydroxide (1 M) and sodium hypochlorite (10,000 and 25,000 mg/L) are very effective in preventing transmission via contaminated wires implanted into animal brains, but their relevance for endoscopes is questionable. Based on circumstantial evidence, it is proposed to consider validated reprocessing as appropriate in the case of delayed suspected prion disease when immediate bedside cleaning, routine use of alkaline cleaners, no fixative agents anywhere prior to disinfection and single use brushes and cleaning solutions can be assured.

Bryophyte stable isotope composition, diversity and biomass define tropical montane cloud forest extent

Liverworts and mosses are a major component of the epiphyte flora of tropical montane forest ecosystems. Canopy access was used to analyse the distribution and vertical stratification of bryophyte epiphytes within tree crowns at nine forest sites across a 3400 m elevational gradient in Peru, from the Amazonian basin to the high Andes. The stable isotope compositions of bryophyte organic material (¹³C/¹²C and ¹⁸O/¹⁶O) are associated with surface water diffusive limitations and, along with C/N content, provide a generic index for the extent of cloud immersion. From lowland to cloud forest δ¹³C increased from -33‰ to -27‰, while δ¹⁸O increased from 16.3‰ to 18.0‰. Epiphytic bryophyte and associated canopy soil biomass in the cloud immersion zone was estimated at up to 45 t dry mass ha^-1, and overall water holding capacity was equivalent to a 20 mm precipitation event. The study emphasizes the importance of diverse bryophyte communities in sequestering carbon in threatened habitats, with stable isotope analysis allowing future elevational shifts in the cloud base associated with changes in climate to be tracked.

Economic and hydraulic divergences underpin ecological differentiation in the Bromeliaceae

Leaf economic and hydraulic theories have rarely been applied to the ecological differentiation of speciose herbaceous plant radiations. The role of character trait divergences and network reorganization in the differentiation of the functional types in the megadiverse Neotropical Bromeliaceae was explored by quantifying a range of leaf economic and hydraulic traits in 50 diverse species. Functional types, which are defined by combinations of C₃ or Crassulacean acid metabolism (CAM) photosynthesis, terrestrial or epiphytic habits, and non-specialized, tank-forming or atmospheric morphologies, segregated clearly in trait space. Most classical leaf economic relationships were supported, but they were weakened by the presence of succulence. Functional types differed in trait-network architecture, suggesting that rewiring of trait-networks caused by innovations in habit and photosynthetic pathway is an important aspect of ecological differentiation. The hydraulic data supported the coupling of leaf hydraulics and gas exchange, but not the hydraulic safety versus efficiency hypothesis, and hinted at an important role for the extra-xylary compartment in the control of bromeliad leaf hydraulics. Overall, our findings highlight the fundamental importance of structure-function relationships in the generation and maintenance of ecological diversity.

Specialized stomatal humidity responses underpin ecological diversity in C3 bromeliads

The Neotropical Bromeliaceae display an extraordinary level of ecological variety, with species differing widely in habit, photosynthetic pathway and growth form. Divergences in stomatal structure and function, hitherto understudied in treatments of bromeliad evolutionary physiology, could have been critical to the generation of variety in ecophysiological strategies among the bromeliads. Because humidity is a key factor in bromeliad niches, we focussed on stomatal responses to vapour pressure deficit (VPD). We measured the sensitivity of stomatal conductance and assimilation rate to VPD in eight C₃ bromeliad species of contrasting growth forms and ecophysiological strategies and parameterised the kinetics of stomatal responses to a step change in VPD. Notably, three tank-epiphyte species displayed low conductance, high sensitivity and fast kinetics relative to the lithophytes, while three xeromorphic terrestrial species showed high conductance and sensitivity but slow stomatal kinetics. An apparent feedforward response of transpiration to VPD occurred in the tank epiphytes, while water-use efficiency was differentially impacted by stomatal closure depending on photosynthetic responses. Differences in stomatal responses to VPD between species of different ecophysiological strategies are closely linked to modifications of stomatal morphology, which we argue has been a pivotal component of the evolution of high diversity in this important plant family.

Unexpected Connections between Humidity and Ion Transport Discovered Using a Model to Bridge Guard Cell-to-Leaf Scales

Stomatal movements depend on the transport and metabolism of osmotic solutes that drive reversible changes in guard cell volume and turgor. These processes are defined by a deep knowledge of the identities of the key transporters and of their biophysical and regulatory properties, and have been modeled successfully with quantitative kinetic detail at the cellular level. Transpiration of the leaf and canopy, by contrast, is described by quasilinear, empirical relations for the inputs of atmospheric humidity, CO2, and light, but without connection to guard cell mechanics. Until now, no framework has been available to bridge this gap and provide an understanding of their connections. Here, we introduce OnGuard2, a quantitative systems platform that utilizes the molecular mechanics of ion transport, metabolism, and signaling of the guard cell to define the water relations and transpiration of the leaf. We show that OnGuard2 faithfully reproduces the kinetics of stomatal conductance in Arabidopsis thaliana and its dependence on vapor pressure difference (VPD) and on water feed to the leaf. OnGuard2 also predicted with VPD unexpected alterations in K+ channel activities and changes in stomatal conductance of the slac1 Cl- channel and ost2 H+-ATPase mutants, which we verified experimentally. OnGuard2 thus bridges the micro-macro divide, offering a powerful tool with which to explore the links between guard cell homeostasis, stomatal dynamics, and foliar transpiration.

Global biogeographic patterns in bipolar moss species

A bipolar disjunction is an extreme, yet common, biogeographic pattern in non-vascular plants, yet its underlying mechanisms (vicariance or long-distance dispersal), origin and timing remain poorly understood. Here, combining a large-scale population dataset and multiple dating analyses, we examine the biogeography of four bipolar Polytrichales mosses, common to the Holarctic (temperate and polar Northern Hemisphere regions) and the Antarctic region (Antarctic, sub-Antarctic, southern South America) and other Southern Hemisphere (SH) regions. Our data reveal contrasting patterns, for three species were of Holarctic origin, with subsequent dispersal to the SH, while one, currently a particularly common species in the Holarctic (Polytrichum juniperinum), diversified in the Antarctic region and from here colonized both the Holarctic and other SH regions. Our findings suggest long-distance dispersal as the driver of bipolar disjunctions. We find such inter-hemispheric dispersals are rare, occurring on multi-million-year timescales. High-altitude tropical populations did not act as trans-equatorial 'stepping-stones', but rather were derived from later dispersal events. All arrivals to the Antarctic region occurred well before the Last Glacial Maximum and previous glaciations, suggesting that, despite the harsh climate during these past glacial maxima, plants have had a much longer presence in this southern region than previously thought.

Stomatal Biology of CAM Plants

Recent advances in the stomatal biology of CAM plants are reviewed, and key opportunities for future progress are identified.

The algal pyrenoid: key unanswered questions

The confinement of Rubisco in a chloroplast microcompartment, or pyrenoid, is a distinctive feature of most microalgae, and contributes to perhaps ~30 Pg of carbon fixed each year, yet our understanding of pyrenoid composition, regulation, and function remains fragmentary. Recently, significant progress in understanding the pyrenoid has arisen from studies using mutant lines, mass spectrometric analysis of isolated pyrenoids, and advanced ultrastructural imaging of the microcompartment in the model alga Chlamydomonas. The emergence of molecular details in other lineages provides a comparative framework for this review, and evidence that most pyrenoids function similarly, even in the absence of a common ancestry. The objective of this review is to explore pyrenoid diversity throughout key algal lineages and discuss whether common ultrastructural and cellular features are indicative of common functional processes. By characterizing pyrenoid origins in terms of mechanistic and structural parallels, we hope to provide key unanswered questions which will inform future research directions.

Pyrenoid loss impairs carbon-concentrating mechanism induction and alters primary metabolism in Chlamydomonas reinhardtii

Carbon-concentrating mechanisms (CCMs) enable efficient photosynthesis and growth in CO2-limiting environments, and in eukaryotic microalgae localisation of Rubisco to a microcompartment called the pyrenoid is key. In the model green alga Chlamydomonas reinhardtii, Rubisco preferentially relocalises to the pyrenoid during CCM induction and pyrenoid-less mutants lack a functioning CCM and grow very poorly at low CO2. The aim of this study was to investigate the CO2 response of pyrenoid-positive (pyr+) and pyrenoid-negative (pyr-) mutant strains to determine the effect of pyrenoid absence on CCM induction and gene expression. Shotgun proteomic analysis of low-CO2-adapted strains showed reduced accumulation of some CCM-related proteins, suggesting that pyr- has limited capacity to respond to low-CO2 conditions. Comparisons between gene transcription and protein expression revealed potential regulatory interactions, since Rubisco protein linker (EPYC1) protein did not accumulate in pyr- despite increased transcription, while elements of the LCIB/LCIC complex were also differentially expressed. Furthermore, pyr- showed altered abundance of a number of proteins involved in primary metabolism, perhaps due to the failure to adapt to low CO2. This work highlights two-way regulation between CCM induction and pyrenoid formation, and provides novel candidates for future studies of pyrenoid assembly and CCM function.