Sex-specific differences and how to handle them in early psoriatic arthritis.

OBJECTIVES: The prevalence of psoriatic arthritis (PsA) is the same in men and women; however, the latter experience a higher burden of disease and are affected more frequently by polyarthritis. Here, we performed an early PsA cohort analysis to assess sex-related differences in demographics, disease characteristics, and evolution over 1 year including applied treatment strategies. METHODS: Our study is embedded in the Dutch south-west Early Psoriatic Arthritis cohoRt. We described patient characteristics and treatment decisions. For the comparison across sexes and baseline and 1 year follow-up, appropriate tests depending on the distribution were used. RESULTS: Two hundred seventy-three men and 294 women with no significant differences in age and ethnicity were included. Women reported significantly longer duration of symptoms before diagnosis and significantly higher tender joint count, a higher disease activity, higher levels of pain, and lower functional capacity. Although minimal disease activity (MDA) rates increased over time for both sexes, MDA remained significantly more prevalent among men at 1 year (58.1% vs 35.7%, p < 0.00). Initially, treatment strategies were similar in both sexes with methotrexate being the most frequently used drug during the first year. Women received methotrexate for a shorter period [196 (93-364) vs 306 (157-365), p < 0.00] and therefore received a lower cumulative dose compared to men. Retention time was shorter for all DMARDs, and women had a delayed start on b-DMARDs. CONCLUSION: After 1 year of standard-of-care treatment, women did not surpass their baseline disadvantages. Despite the overall improvement, they still presented higher disease activity, higher levels of pain, and lower functional capacity score than men. The nature of these findings may advocate a need for sex specific adjustment of treatment strategies and evaluation in early PsA patients.

Usage of C-Reactive Protein Testing in the Diagnosis and Monitoring of Psoriatic Arthritis (PsA): Results from a Real-World Survey in the USA and Europe.

INTRODUCTION: C-reactive protein (CRP) is an important non-specific marker of both acute and chronic inflammation and can be elevated in patients with psoriatic arthritis (PsA). However, the use of CRP testing in the management of PsA can vary. This study investigated how CRP testing is implemented in real-world clinical practice for disease management of PsA. METHODS: A point-in-time survey of rheumatologists and dermatologists and their next six consulting patients with PsA was conducted in France, Germany, Italy, Spain, UK (EU5), and the USA between June and August 2018. Use of CRP testing was obtained by asking the physician to state (yes/no) whether CRP was used to aid PsA diagnosis and/or to monitor the patient's disease activity. The number of CRP tests conducted in the last 12 months for each patient enrolled was provided. RESULTS: Data were collected for 2270 patients (USA, n = 595; EU5, n = 1675). In the EU5, CRP testing was conducted to aid diagnosis in 78.7% of patients (vs. 43.4% in USA) and CRP was used to monitor disease activity in 72.0% (vs. 34.6% in USA). The majority (80.9%) of patients in the EU5 had at least one CRP test in the last 12 months compared to 42.9% in the USA. Patients treated by rheumatologists (vs. dermatologists) were at least 50% more likely to have CRP tested for monitoring purposes, this difference being most pronounced in the USA. In the EU5, CRP testing was conducted a mean ± standard deviation of 2.7 ± 1.7 times during the last 12 months, versus 2.0 ± 1.4 in the USA. CONCLUSIONS: CRP was more commonly used for the diagnosis and monitoring of PsA in Europe compared to the USA and was more commonly ordered by rheumatologists than dermatologists. In the absence of a better serum biomarker of inflammation, more data are needed to understand how CRP testing should be used in the diagnosis and management PsA.

Comparing the efficacy and tolerability of biologic therapies in psoriasis: an updated network meta-analysis.

BACKGROUND: The rapid expansion of psoriasis biologics has led to an urgent need to understand their relative efficacy and tolerability to inform treatment decisions better and, specifically, to inform guideline development. OBJECTIVES: To update a 2017 meta-analysis on the comparative efficacy and tolerability of biologic treatments for psoriasis. METHODS: We searched the MEDLINE, PubMed, Embase and Cochrane databases for randomized controlled trials (RCTs), published up to 7 September 2018, of 11 licensed, NICE-approved biologics targeting tumour necrosis factor (adalimumab, etanercept, infliximab, certolizumab pegol), interleukin (IL)-12/IL-23p40 (ustekinumab), IL-17A (secukinumab, ixekizumab), IL-17RA (brodalumab) and IL-23p19 (guselkumab, tildrakizumab, risankizumab). A frequentist network meta-analysis ascertained direct or indirect evidence comparing biologics with one another, methotrexate or placebo. This was combined with hierarchical cluster analyses to consider efficacy (≥ 90% improvement in Psoriasis Area and Severity Index (PASI 90) or Physician's Global Assessment 0 or 1; PASI 75; Dermatology Life Quality Index improvement) and tolerability (drug withdrawal due to adverse events) outcomes at 10-16 weeks, followed by assessments of study quality, heterogeneity and inconsistency. RESULTS: We identified 62 RCTs presenting data on direct comparisons (31 899 participants). All biologics were efficacious compared with placebo or methotrexate at 10-16 weeks. Hierarchical cluster analyses revealed that adalimumab, brodalumab, certolizumab pegol, guselkumab, risankizumab, secukinumab, tildrakizumab and ustekinumab were comparable with respect to high short-term efficacy and tolerability. Infliximab and ixekizumab clustered together, with high short-term efficacy but relatively lower tolerability than the other agents, although the number of drug withdrawal events across the network was low, so these findings should be treated with caution. CONCLUSIONS: Using our methodology we found that most biologics cluster together with respect to short-term efficacy and tolerability, and we did not identify any single agent as 'best'. These data need to be interpreted in the context of longer-term efficacy, effectiveness data, safety, posology and drug acquisition costs when making treatment decisions.

Results of a global, patient-based survey assessing the impact of psoriatic arthritis discussed in the context of the Psoriatic Arthritis Impact of Disease (PsAID) questionnaire.

BACKGROUND: Psoriatic arthritis (PsA) is a chronic immune-mediated inflammatory musculoskeletal disease, manifesting as peripheral arthritis, enthesitis, dactylitis, spondylitis, and skin and nail psoriasis. A core set of domains for measuring the impact of PsA has been developed, including pain, patient global assessment, physical function, health-related quality of life (HRQoL), and fatigue. To understand the impact of PsA on health domains from a patient's perspective, a global survey was developed and results reported in the context of the 12-item Psoriatic Arthritis Impact of Disease (PsAID-12) questionnaire. METHODS: An online patient-based global survey was conducted by The Harris Poll in Australia, Brazil, Canada, France, Spain, Taiwan, the UK, and the US between November 2, 2017 and March 12, 2018. Eligible patients were ≥ 18 years old with a diagnosis of PsA for > 1 year, had visited a rheumatologist/dermatologist in the past 12 months and reported using ≥ 1 synthetic/biologic disease-modifying antirheumatic drug for PsA. Patients reported on PsA severity and symptoms, and the impact of PsA on HRQoL. After survey completion, responses were aligned with PsAID health domains. Descriptive statistics and chi-square tests were conducted. RESULTS: This analysis included 1286 patients from eight countries. Most patients (97%) reported musculoskeletal symptoms relating to PsA in the past year. Common moderate/major impacts of PsA were on physical activity (78%), ability to perform certain activities (76%), work productivity (62%), and career path (57%). Skin/nail symptoms occurred in 80% of patients. Overall, 69% of patients reported that PsA had a moderate/major impact on emotional/mental wellbeing, 56% on romantic relationships/intimacy, and 44% on relationships with family and friends. Social impacts included emotional distress (58%), social shame or disapproval (32%), and ceased participation in social activities (45%). Over half of all patients experienced unusual fatigue over the past 12 months (52%). The health domains that patients reported as being impacted by PsA aligned with life impact domains of the patient-derived PsAID health domains. CONCLUSION: These results highlight the impact of PsA on multiple health domains from a patient perspective that should be considered during shared decision-making processes between healthcare providers and patients.

Long-term efficacy and safety of secukinumab in the treatment of the multiple manifestations of psoriatic disease.

Psoriatic disease is a multifaceted disorder, which develops in the skin, its appendages and joints. Though characterized by different pathogenic background and clinical manifestations, skin plaque psoriasis (PsO), psoriatic arthritis (PsA) and ankylosing spondylitis (AS) are related, sharing key inflammatory mechanisms and hence mode of management. Secukinumab is a fully human monoclonal antibody that selectively binds and neutralizes interleukin-17A. It has been approved for use as a subcutaneous injection for the treatment of moderate-to-severe PsO, PsA and AS. The current review highlights the long-term efficacy and safety profile of secukinumab in the treatment of plaque psoriasis and its multiple manifestations from its phase 3 clinical trial programme. The long-term extension of pivotal trials has shown sustainable efficacy and safety of secukinumab up to 5 years in PsO, PsA and AS and up to 2.5 years in moderate-to-severe nail and palmoplantar PsO through dedicated randomized controlled trials. The effect of secukinumab therapy in all these indications has corresponding effects on improvement in quality-of-life and daily activities. Overall, secukinumab is an effective and safe treatment choice for patients suffering from psoriatic disease in its multiple clinical variants.

Secukinumab provides sustained PASDAS-defined remission in psoriatic arthritis and improves health-related quality of life in patients achieving remission: 2-year results from the phase III FUTURE 2 study.

BACKGROUND: Secukinumab has demonstrated sustained improvement in the signs and symptoms of psoriatic arthritis (PsA) over 2 years in the FUTURE 2 study (NCT01752634). This post hoc analysis assessed the ability of secukinumab to achieve Psoriatic Arthritis Disease Activity Score (PASDAS)-based remission or low disease activity (LDA) through 2 years among patients with PsA in the FUTURE 2 study. METHODS: PASDAS (cut-off scores: remission ≤ 1.9; LDA > 1.9 and < 3.2; Moderate Disease Activity ≥ 3.2 and < 5.4; and high disease activity [HDA] ≥ 5.4) was assessed in the overall population (tumour necrosis factor inhibitor [TNFi]-naïve and TNFi-experienced), in patients stratified by prior TNFi use and by disease duration at weeks 16, 52 and 104. The impact of secukinumab on individual PASDAS core components and on the relationship between PASDAS states and patient-reported outcomes (PROs), including physical function, health-related quality of life (HRQoL) and work productivity, were also assessed. Data for the approved doses of secukinumab (300 and 150 mg) are reported. PASDAS scores and core components were reported as observed, and PROs were analysed using mixed models for repeated measures. RESULTS: In the overall population, PASDAS remission and LDA were achieved in 15.6% and 22.9%, respectively, of patients treated with secukinumab 300 mg and in 15.2% and 19.2%, respectively, in the secukinumab 150 mg group versus 2.3% and 13.8%, respectively, with placebo at week 16. In the TNFi-naïve group, a higher proportion of patients achieved remission + LDA at week 16 with secukinumab 300 and 150 mg (46.2% and 42.9%, respectively) versus placebo (17.5%), with corresponding responses in TNFi-experienced patients being 22.6% and 19.4% versus 13.3%. Remission/LDA responses with secukinumab were sustained through 2 years. Patients achieving remission/LDA reported greater improvements in PROs than patients in HDA through 2 years. CONCLUSIONS: Secukinumab-treated patients achieved higher PASDAS-defined remissions or LDA compared with placebo at week 16, which were sustained through 2 years. Remission/LDA was achieved by both TNFi-naïve and TNFi-experienced patients treated with secukinumab, with higher rates in TNFi-naïve patients. Secukinumab-treated patients achieving remission/LDA reported significantly greater improvements in PROs, including physical function and different dimensions of health-related quality of life and work, than patients in HDA. TRIAL REGISTRATION: ClinicalTrials.gov, NCT01752634 . Registered on December 19, 2012. EUDRACT, 2012-004439-22 . Registered on December 12, 2012.

Assessment of two screening tools to identify psoriatic arthritis in patients with psoriasis.

BACKGROUND: Many patients with psoriasis have undiagnosed psoriatic arthritis. Low specificity is found with many PsA screening tools. A new instrument, the CONTEST questionnaire, was developed utilizing the most discriminative items from existing instruments. OBJECTIVE: The aim of this study was to compare the CONTEST and PEST screening tools. METHODS: People attending secondary care clinics with psoriasis, but not PsA, completed the questionnaires, were assessed for function and quality of life, and had a physical examination. Patients thought to have PsA were compared to those without. The performance of CONTEST and PEST was compared using area under the receiver operating curve (AUC), and sensitivity and specificity at the previously published cut-offs. RESULTS: A total of 451 dermatology patients were approached, 35% were reviewed and 27 (17%, 95% CI 12.3-21.7) had unidentified psoriatic arthritis. The sensitivity and specificity (95% CI) of PEST were 0.60 (0.42-0.78)/0.76 (0.69-0.83) and for CONTEST 0.53 (0.34-0.72)/0.71 (0.63-0.79). The confidence limits for the AUC overlapped (AUC for PEST 0.72 (0.61-0.84), for CONTEST 0.66 (0.54-0.77). CONCLUSIONS: PEST and CONTEST questionnaires performed equally well, with no superiority of the new CONTEST tool.

Comparison of screening questionnaires to identify psoriatic arthritis in a primary-care population: a cross-sectional study.

BACKGROUND: Many questionnaires are available for assessment of psoriatic arthritis (PsA), but there is little evidence comparing them. OBJECTIVES: To test the proposed CONTEST questionnaire, which was developed to identify patients with psoriasis who have undiagnosed PsA, and compare it with the validated Psoriasis Epidemiology Screening Tool (PEST) questionnaire in a primary-care setting. METHODS: A random sample of adult patients with psoriasis and no diagnosis of arthritis was identified from five general practice surgeries in Yorkshire, U.K. Consenting patients completed both questionnaires and were assessed by a dermatologist and rheumatologist. Diagnosis of PsA was made by the assessing rheumatologist. Receiver operator characteristic (ROC) curve analysis examined the sensitivity and specificity of potential cut points. RESULTS: In total 932 packs were sent to recruit 191 (20·5%) participants. Of these, 169 (88·5%) were confirmed to have current or previous psoriasis. Using physician diagnosis 17 (10·1%) were found to have previously undiagnosed PsA, while 90 (53·3%) had another musculoskeletal complaint and 62 (36·7%) had no musculoskeletal problems. Using ROC curve analysis, all of the questionnaires showed a significant ability to identify PsA. The area under the curve (AUC) for the CONTEST questionnaires was slightly higher than that of PEST (0·69 and 0·70 vs. 0·65), but there was no significant difference identified. Examining the sensitivities and specificities for the different cut points suggested that a PEST score ≥ 2 would perform better in this dataset, and the optimal scores for CONTEST and CONTEST plus joint manikin were 3 and 4, respectively. CONCLUSIONS: The accuracy of the questionnaires to identify PsA appeared similar, with a slightly higher AUC for the CONTEST questionnaires. The optimal cut points in this study appeared lower than in previous studies.

Optimisation of rheumatology indices: dactylitis and enthesitis in psoriatic arthritis.

Outcome measures are a key part of study design and clinical assessment. Enthesitis and dactylitis are typical features of psoriatic arthritis (PsA) and the spondyloarthritides but traditionally scoring systems for enthesitis have mainly been validated in ankylosing spondylitis (AS). There are many scoring systems which are not validated used for dactylitis although newer validated scores are now available. Recently there have been advances in composite scores that include enthesitis and dactylitis to assess disease activity. These are currently being validated further and have not yet been tested in routine clinical practice.

Comparison of three screening tools to detect psoriatic arthritis in patients with psoriasis (CONTEST study).

BACKGROUND: Multiple questionnaires to screen for psoriatic arthritis (PsA) have been developed but the optimal screening questionnaire is unknown. OBJECTIVES: To compare three PsA screening questionnaires in a head-to-head study using CASPAR (the Classification Criteria for Psoriatic Arthritis) as the gold standard. METHODS: This study recruited from 10 U.K. secondary care dermatology clinics. Patients with a diagnosis of psoriasis, not previously diagnosed with PsA, were given all three questionnaires. All patients who were positive on any questionnaire were invited for a rheumatological assessment. Receiver operating characteristic (ROC) curves were used to compare the sensitivity, specificity and area under the curve of the three questionnaires according to CASPAR criteria. RESULTS: In total, 938 patients with psoriasis were invited to participate and 657 (70%) patients returned the questionnaires. One or more questionnaires were positive in 314 patients (48%) and 195 (62%) of these patients attended for assessment. Of these, 47 patients (24%) were diagnosed with PsA according to the CASPAR criteria. The proportion of patients with PsA increased with the number of positive questionnaires (one questionnaire, 19·1%; two, 34·0%; three, 46·8%). Sensitivities and specificities for the three questionnaires, and areas under the ROC curve were, respectively: Psoriatic Arthritis Screening Evaluation (PASE), 74·5%, 38·5%, 0·594; Psoriasis Epidemiology Screening Tool (PEST), 76·6%, 37·2%, 0·610; Toronto Psoriatic Arthritis Screen (ToPAS), 76·6%, 29·7%, 0·554. The majority of patients with a false positive response had degenerative or osteoarthritis. CONCLUSION: Although the PEST and ToPAS questionnaires performed slightly better than the PASE questionnaire at identifying PsA, there is little difference between these instruments. These screening tools identify many cases of musculoskeletal disease other than PsA.

Is there subclinical enthesitis in early psoriatic arthritis? A clinical comparison with power doppler ultrasound.

OBJECTIVE: Enthesitis is a recognized feature of spondylarthritides (SpA), including psoriatic arthritis (PsA). Previously, ultrasound imaging has highlighted the presence of subclinical enthesitis in established SpA, but there are little data on ultrasound findings in early PsA. The aim of our study was to compare ultrasound and clinical examination (CE) for the detection of entheseal abnormalities in an early PsA cohort. METHODS: Forty-two patients with new-onset PsA and 10 control subjects underwent CE of entheses for tenderness and swelling, as well as gray-scale (GS) and power Doppler (PD) ultrasound of a standard set of entheses. Bilateral elbow lateral epicondyles, Achilles tendons, and plantar fascia were assessed by both CE and ultrasound, the latter scored using a semiquantitative (SQ) scale. Inferior patellar tendons were assessed by ultrasound alone. A GS SQ score of >1 and/or a PD score of >0 was used to describe significant ultrasound entheseal abnormality. RESULTS: A total of 24 (57.1%) of 42 patients in the PsA group and 0 (0%) of 10 controls had clinical evidence of at least 1 tender enthesis. In the PsA group, for sites assessed by both CE and ultrasound, 4% (7 of 177) of nontender entheses had a GS score >1 and/or a PD score >0 compared to 24% (9 of 37) of tender entheses. CE overestimated activity in 28 (13%) of 214 of entheses. All the nontender ultrasound-abnormal entheses were in the lower extremity. CONCLUSION: The prevalence of subclinical enthesitis in this early PsA cohort was low. CE may overestimate active enthesitis. The few subclinically inflamed entheses were in the lower extremity, where mechanical stress is likely to be more significant.

Defining minimal disease activity in psoriatic arthritis: a proposed objective target for treatment.

OBJECTIVE: To create minimal disease activity (MDA) criteria for psoriatic arthritis (PsA). With recent therapeutic advances, this is now a goal for treatment and may represent a measure to compare therapies. It defines a satisfactory state of disease activity rather than a change, and encompasses all aspects of the disease. METHODS: 40 patient profiles were sampled from an observational PsA database. Sixty experts in PsA classified these as in MDA or not. A consensus of > or =70% was accepted, identifying 13 profiles in MDA. Summary statistics created possible cut-off points for the definition. Considering the number of measures that must be met, 35 candidate definitions were created and tested using receiver operating characteristic curves (ROC) for sensitivity and specificity. RESULTS: Four candidate definitions showed high area under the curve values on ROC testing. Definitions with high outlying values were excluded as they were not considered to represent MDA. Aiming for high specificity to reduce false positives resulted in a preference for the following definition: "A patient is classified as achieving MDA when meeting 5 of the 7 following criteria: tender joint count < or =1; swollen joint count < or =1; Psoriasis Activity and Severity Index < or =1 or body surface area < or =3; patient pain visual analogue score (VAS) < or =15; patient global disease activity VAS < or =20; health assessment questionnaire < or =0.5; tender entheseal points < or =1". CONCLUSION: This study provides the first definition of a "state" of MDA in PsA and defines a target for treatment. It must now be validated in other populations and tested in clinical trials.

Real life experience confirms sustained response to long-term biologics and switching in ankylosing spondylitis.

OBJECTIVE: To investigate the long-term response to biological therapies in AS in a real life clinical setting and to quantify non-response and response to 'switching' therapies in these cases. METHODS: All patients prescribed TNF-blocking therapies for AS between 1999 and 2006 were studied. Response was evaluated using Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Bath Ankylosing Spondylitis Functional Index (BASFI) and CRP results. RESULTS: A total of 113 patients (84 males: 29 females, mean age 45 yrs, median disease duration 16 yrs, 87% HLA-B27 positive) were identified. At baseline they had a mean BASDAI of 6.57, BASFI 6.57 and CRP of 31 g/dl. At the end of follow-up, these values had reduced to mean BASDAI of 3.12, BASFI 4.16 and CRP of 7 g/dl. Improvements were sustained for 24 months and beyond with no loss of effect. Only nine patients (8%) suffered side-effects leading to cessation or switching of first-line therapy and non-response occurred in 15 patients (13%) in the long term. Fifteen patients (13%) switched to a second drug and 14 of these (93%) had a significant and sustained response. Outcomes were similar regardless of drug used, duration of disease and HLA-B27 status. CONCLUSION: Treatment of active AS with TNF blockers according to the British Society of Rheumatology guidelines leads to a sustained response for over 2 yrs with most patients tolerating the drugs well. The rate of non-response is significantly lower than that seen in RA and nearly all of these patients respond well to a second-line agent.

Sustained response to long-term biologics and switching in psoriatic arthritis: results from real life experience.

OBJECTIVE: To investigate the response to biologic drugs in psoriatic arthritis and to quantify non-response and outcome from switching agents. METHODS: 60 patients (33 men and 27 women, mean age 46 years, median disease duration 16 years) prescribed biologic drugs for psoriatic arthritis between 2001 and 2006 were studied. Response was evaluated using joint counts, C-reactive protein levels and disease activity scores (using 28 joints; DAS28). RESULTS: The mean percentage improvements seen were 56% in tender joint count, 70% in swollen joint count, 64% in C-reactive protein level and 36% in the overall disease activity score. Improvements were sustained beyond 24 months with no loss of effect. Side-effects leading to cessation or switching of first-line therapy were only seen in 5% of patients and non-response occurred in 20% long term. Overall, 90% of patients achieved a significant response, using switching in 20% of cases. Outcomes were similar regardless of drug used, duration of disease and subtype of arthritis. CONCLUSIONS: Treatment of active psoriatic arthritis with anti-tumour necrosis factor agents leads to a sustained response over 3 years with most patients tolerating these drugs well. The rate of non-response is low with the majority of patients responding to second- and third-line therapies.

Neuroserpin is expressed in the pituitary and adrenal glands and induces the extension of neurite-like processes in AtT-20 cells.

Two cDNAs encoding the serine protease inhibitor (serpin) neuroserpin were cloned from a rat pituitary cDNA library (rNS-1, 2922 bp; rNS-2, 1599 bp). In situ hybridization histochemistry showed neuroserpin transcripts in the intermediate, anterior and posterior lobes of the pituitary gland and medullary cells in the adrenal gland. Expression of rNS-1 mRNA was restricted to selected cells in the pituitary gland. Analysis of purified secretory-granule fractions from pituitary and adrenal tissues indicated that neuroserpin was found in dense-cored secretory granules. This result suggested that endocrine neuroserpin may regulate intragranular proteases or inhibit enzymes following regulated secretion. To investigate the function of neuroserpin in endocrine tissues we established stable anterior pituitary AtT-20 cell lines expressing neuroserpin. Cells with increased levels of neuroserpin responded by extending neurite-like processes. Extracellular proteolysis by serine protease plasminogen activators has been suggested to regulate neurite outgrowth. As neuroserpin inhibits tissue plasminogen activator (tPA) in vitro, we measured plasminogen-activator levels. Zymographic analysis indicated that AtT-20 cells synthesized and secreted a plasminogen activator identical in size to tPA. A higher-molecular-mass tPA-neuroserpin complex was also observed in AtT-20-cell conditioned culture medium. tPA levels were similar in parent AtT-20 cells and a stable cell line with increased levels of neuroserpin. There was no accumulation of a tPA-neuroserpin complex. Together these results identify endocrine cells as an important source of neuroserpin. Moreover they suggest that neuroserpin is released from dense-cored secretory granules to regulate cell-extracellular matrix interactions through a mechanism that may not directly involve tPA.

Posttranslational maturation of the prohormone convertase SPC3 in vitro.

The subtilisin-like prohormone convertase SPC3 is likely to play a role in the biosynthesis of a variety of biologically active peptides. SPC3 undergoes a series of posttranslational processing events during its biosynthesis. Multiple forms have been identified that show varying degrees of truncation at the carboxyl terminus. In this study we show that the 86-kDa form of recombinant SPC3 with an intact carboxyl terminus can undergo rapid carboxyl-terminus truncation to produce a 64-kDa form. We have defined the optimal conditions for carboxyl-terminus truncation in vitro. The carboxyl-terminus truncation reaction was less calcium sensitive, active over a broader pH range, and showed differences in inhibitor sensitivity compared with the enzymatic activities of full-length and truncated forms of SPC3 toward a fluorescent peptide substrate. Increases in enzymatic activity of 86-kDa SPC3 were also measured over a time frame consistent with conversion to the 64-kDa form. However, similar specific activities for both forms of the enzyme suggest such activity increases may not be due to carboxyl-terminus truncation. The different enzymatic properties of the major molecular forms of SPC3 highlight the importance of understanding the molecular events regulating carboxyl-terminal processing of this endoprotease.