The association between sonographic enthesitis with sonographic synovitis and tenosynovitis in psoriatic arthritis patients.

OBJECTIVES: To examine the association between sonographic enthesitis with sonographic synovitis and tenosynovitis in PsA patients, and the association between sonographic enthesitis and clinical characteristics. METHODS: Consecutive PsA patients that fulfilled the ClASsification criteria for Psoriatic ARthritis (CASPAR) were prospectively recruited. Each patient was evaluated by comprehensive clinical and sonographic assessment (greyscale and Doppler), the latter including 52 joints, 40 tendons and 14 entheses [according to MAdrid Sonography Enthesitis Index (MASEI) plus lateral epicondyles] performed by an experienced sonographer blinded to the clinical data. The US enthesitis score was further categorized to inflammatory (hypoechogenicity, thickening, bursitis and Doppler) and structural (enthesophytes/calcifications and erosions) subcategories. Multivariate linear regression models assessed the association between enthesitis and the selected variables. RESULTS: A total of 158 PsA patients [mean (s.d.) age 52.3 (13) years, 88 (55.7%) females] were analysed. Multivariate linear regression analyses showed a significant association between sonographic enthesitis and sonographic synovitis (ß = 0.18, P = 0.008) and between sonographic enthesitis and sonographic tenosynovitis (ß = 0.06, P = 0.02). These associations were derived from the enthesitis inflammatory subcategory of the MASEI (P < 0.05). Associations between enthesitis and synovitis were also demonstrated on the level of the elbow, knee and ankle joints (P < 0.05). In addition, sonographic enthesitis was significantly associated with older age, male sex, swollen joint count, CRP level and physical occupation. CONCLUSIONS: Sonographic enthesitis is associated with sonographic synovitis and tenosynovitis. The severity of sonographic enthesitis may represent a marker for inflammatory activity in other musculoskeletal domains.

Systemic Lupus Erythematous and Obstructive Sleep Apnea: A Possible Association.

Marked fatigue is common in patients with systemic lupus erythematosus (SLE). This study aimed to assess the association of sleep disorders, including obstructive sleep apnea (OSA), with SLE. Forty-two consecutive patients with SLE and 20 healthy controls were recruited and underwent a one-night ambulatory sleep examination. They completed questionnaires, including the Pittsburgh Sleep Quality Index (PSQI) and Functional Assessment of Chronic Illness Therapy (FACIT). SLE disease activity and damage were assessed by the SLE Disease Activity Index 2000 (SLEDAI-2K) and the Systemic Lupus International Collaborating Clinics/American College of Rheumatology (SLICC/ACR) damage index (SDI). A significantly increased apnea/hypopnea index was noted in the SLE group compared to healthy controls (p = 0.004). SLE patients had higher rates of moderate-to-severe OSA (p = 0.04), PSQI (p = 0.001), and FACIT scores (p = 0.0008). Multivariate analysis revealed that the SDI was associated with OSA (p = 0.03). There was a positive association between SLEDAI-2K and moderate-to-severe OSA (p = 0.03). Patients with SLE had an increased prevalence of OSA and poorer quality of sleep compared to healthy controls. Our findings suggest that active disease and accumulated damage may be associated with OSA. These findings highlight the importance of identifying the presence of OSA in patients with SLE.

Sex-Based Differences in Sonographic and Clinical Findings Among Patients With Psoriatic Arthritis.

OBJECTIVE: To investigate sex-based sonographic differences in patients with psoriatic arthritis (PsA). METHODS: The study population included consecutive prospectively recruited patients with PsA, as determined by the CASPAR (Classification for Psoriatic Arthritis) criteria, who underwent clinical and physical examinations, followed by a detailed ultrasound (US) evaluation (greyscale and Doppler). US evaluation included 52 joints, 40 tendons, and 14 points of entheses (Modified Madrid Sonographic Enthesis Index [MASEI] plus lateral epicondyles) performed by an experienced sonographer blinded to the clinical data. The US score was based on the summation of a semiquantitative score for synovitis, tenosynovitis, and enthesitis. The US enthesitis score was categorized into inflammatory lesions (ie, hypoechogenicity, thickening, bursitis, and Doppler) and structural lesions (ie, enthesophytes/calcifications and erosions). RESULTS: The study population of 158 patients included 70 males and 88 females. The males had higher rates of employment (P = 0.01), Psoriasis Area and Severity Index scores (P = 0.04), and mean swollen joint counts (P = 0.04). The total US score and its subcategory scores-the synovitis and tenosynovitis scores-were similar for both sexes, whereas the total enthesitis score and its subcategory score-the inflammatory enthesitis score-were significantly higher for the males compared to the females (P = 0.01 and P = 0.005, respectively). Hypoechogenicity, thickening, and enthesophytes were more prevalent in males compared to females (P < 0.05). Multivariate ordinal logistic regression models showed that male sex was associated with a higher US inflammatory enthesitis score compared to female sex (odds ratio 1.96, P = 0.02). CONCLUSION: Sonographic enthesitis was more prevalent in males compared to females with PsA. These differences were not reflected by enthesitis disease activity scores derived from clinical assessment.

Ultrasound, magnetic resonance imaging and radiography of the finger joints in psoriatic arthritis patients.

OBJECTIVES: To report the discrepancies and agreements between US, MRI and radiography of the hand in PsA, and to compare the sensitivity and specificity of US and radiography to MRI as the gold standard imaging study in PsA. METHODS: All of the 100 prospectively recruited consecutive PsA patients underwent clinical assessment and concomitant radiographic, US and MRI studies of the MCP, PIP and DIP joints of one hand. Synovitis, flexor tenosynovitis, extensor paratenonitis, erosions and bone proliferations were identified and scored. All readers were blinded to clinical data, and agreement was calculated based on prevalence-adjusted bias-adjusted kappa (PABAK). RESULTS: The prevalence of synovitis, flexor tenosynovitis, extensor paratenonitis and erosions was similar for US and MRI, while that of bone proliferation was significantly increased in US and radiography compared with MRI (P < 0.001). The absolute agreement between US and MRI was good-to-very good for synovitis (85-96%, PABAK = 0.70-0.92), flexor tenosynovitis (93-98%, PABAK = 0.87-0.96) and extensor paratenonitis (95-98%, PABAK = 0.90-0.97). Agreement between US, MRI and radiography was 96-98% (PABAK = 0.92-0.97) for erosions and 71-93% (PABAK = 0.47-0.87) for bone proliferations. Sensitivity of US with MRI as gold standard was higher for synovitis (0.5-0.86) and extensor paratenonitis (0.63-0.85) than for flexor tenosynovitis (0.1-0.75), while the specificity was high for each pathology (0.89-0.98). CONCLUSION: There is very good agreement between US and MRI for the detection of inflammatory changes in finger joints in PsA. US, radiography and MRI have a good-to-very good agreement for destructive changes.

Role of ultrasound for assessment of psoriatic arthritis patients with fibromyalgia.

OBJECTIVE: To investigate whether ultrasonography (US), as an objective imaging modality, can optimise the evaluation of disease activity in psoriatic arthritis (PsA) patients with concomitant fibromyalgia syndrome (FMS). METHODS: The study population included 156 consecutive PsA patients who were recruited prospectively and fulfilled the ClASsification criteria for Psoriatic ARthritis criteria. The patients underwent complete clinical evaluation including assessment of fulfilment of the 2016 fibromyalgia classification criteria. All of the patients underwent US evaluation including 52 joints, 40 tendons and 14 entheses. The US score was based on the summation of a semiquantitative score (including synovitis, tenosynovitis and enthesitis). Scoring was performed by a sonographer blinded to the clinical data. Spearman's correlation coefficient and multivariate linear regression models were used to examine the association of FMS with clinical and the US scores. RESULTS: Forty-two patients (26.9%) with coexisting PsA and FMS were compared with 114 (73.1%) PsA patients without FMS. Patients with PsA and FMS had significantly increased scores for clinical composite indices, including non-Minimal Disease Activity, Composite Psoriatic Disease Activity Index (CPDAI), Disease Activity for Psoriatic Arthritis (DAPSA) and Psoriatic Arthritis Disease Activity Score (PASDAS) (p<0.001). In contrast, the total US score and its subcategories were similar for those with and without FMS. The total US score significantly correlated with CPDAI, DAPSA and PASDAS (p<0.001) in the PsA without FMS but not in the PsA with FMS group. FMS was significantly associated with higher clinical scores (p<0.001) but not with the US score (multivariable linear regression models). CONCLUSIONS: US has significantly greater value than composite clinical scores in the assessment of disease activity in PsA patients with FMS.

Immunogenicity and safety of the BNT162b2 mRNA COVID-19 vaccine in adult patients with autoimmune inflammatory rheumatic diseases and in the general population: a multicentre study.

INTRODUCTION: Vaccination represents a cornerstone in mastering the COVID-19 pandemic. Data on immunogenicity and safety of messenger RNA (mRNA) vaccines in patients with autoimmune inflammatory rheumatic diseases (AIIRD) are limited. METHODS: A multicentre observational study evaluated the immunogenicity and safety of the two-dose regimen BNT162b2 mRNA vaccine in adult patients with AIIRD (n=686) compared with the general population (n=121). Serum IgG antibody levels against SARS-CoV-2 spike S1/S2 proteins were measured 2-6 weeks after the second vaccine dose. Seropositivity was defined as IgG ≥15 binding antibody units (BAU)/mL. Vaccination efficacy, safety, and disease activity were assessed within 6 weeks after the second vaccine dose. RESULTS: Following vaccination, the seropositivity rate and S1/S2 IgG levels were significantly lower among patients with AIIRD versus controls (86% (n=590) vs 100%, p<0.0001 and 132.9±91.7 vs 218.6±82.06 BAU/mL, p<0.0001, respectively). Risk factors for reduced immunogenicity included older age and treatment with glucocorticoids, rituximab, mycophenolate mofetil (MMF), and abatacept. Rituximab was the main cause of a seronegative response (39% seropositivity). There were no postvaccination symptomatic cases of COVID-19 among patients with AIIRD and one mild case in the control group. Major adverse events in patients with AIIRD included death (n=2) several weeks after the second vaccine dose, non-disseminated herpes zoster (n=6), uveitis (n=2), and pericarditis (n=1). Postvaccination disease activity remained stable in the majority of patients. CONCLUSION: mRNA BNTb262 vaccine was immunogenic in the majority of patients with AIIRD, with an acceptable safety profile. Treatment with glucocorticoids, rituximab, MMF, and abatacept was associated with a significantly reduced BNT162b2-induced immunogenicity.

Prevalence of Nonradiographic Sacroiliitis in Patients With Psoriatic Arthritis: A Real-life Observational Study.

OBJECTIVE: To establish the prevalence of nonradiographic sacroiliitis within a real-life sample of patients with psoriatic arthritis (PsA), using pelvic radiographs and magnetic resonance imaging (MRI) of sacroiliac joints (SIJs). METHODS: This cross-sectional study included 107 consecutive adults with PsA (Classification Criteria for Psoriatic Arthritis criteria). Participants completed clinical and laboratory evaluation, pelvic radiographs scored for radiographic sacroiliitis according to the modified New York (mNY) criteria, and noncontrast MRI of SIJs, scored by the Berlin score and categorized into active sacroiliitis using the 2016 Assessment of Spondyloarthritis international Society (ASAS) criteria and the presence of structural sacroiliitis. RESULTS: Radiographic sacroiliitis/mNY criteria were detected in 28.7% (n = 29), confirmed by MRI-detected structural lesions in 72.4% (n = 21). Active sacroiliitis was detected by MRI in 26% (n = 28) of patients, with 11% (n = 11) qualifying for nonradiographic sacroiliitis. Patients with radiographic and nonradiographic sacroiliitis had similar clinical characteristics, except for a longer duration of psoriasis (PsO) and PsA in the radiographic subgroup (PsO: 23.8 ± 12.5 vs 14.1 ± 11.7 yrs, P = 0.03; PsA: 12.3 ± 9.8 vs 4.7 ± 4.5 yrs, P = 0.02, respectively). Inflammatory back pain (IBP) was reported in 46.4% (n = 13) with active sacroiliitis and 27% (n = 3) with nonradiographic sacroiliitis. The sensitivity of IBP for detection of nonradiographic sacroiliitis was low (27%) and moderate for radiographic sacroiliitis (52%), whereas specificity ranged from 72% to 79% for radiographic and nonradiographic sacroiliitis, respectively. CONCLUSION: The prevalence of active sacroiliitis among a real-life population of patients with PsA was 26%. However, the prevalence of nonradiographic sacroiliitis was low (11%) compared to the radiographic sacroiliitis (28.7%) seen in patients with longer disease duration. IBP was not a sensitive indicator for the presence of early-stage sacroiliitis that was commonly asymptomatic.

Soluble ST2 and CXCL-10 may serve as biomarkers of subclinical diastolic dysfunction in SLE and correlate with disease activity and damage.

OBJECTIVE: Subclinical myocardial dysfunction has been reported to occur early in systemic lupus erythematous (SLE). The study aim was to search for biomarkers of subclinical myocardial dysfunction which may correlate with disease activity in SLE patients. METHODS: This is a prospective, controlled, cross-sectional study of 57 consecutive patients with SLE and 18 controls. Serum samples were obtained to determine serum soluble ST2 (sST2), CXCL-10 and high-sensitivity troponin (hs-troponin) levels. All participants underwent an echocardiographic tissue Doppler study. RESULTS: sST2, CXCL-10 and hs-troponin levels were higher in patients with higher SLE disease activity (SLEDAI). sST2 and CXCL-10 levels were higher in patients with more disease damage as measured by the SLE damage index. Measures of diastolic dysfunction, as assessed by echocardiographic tissue Doppler negatively correlated with log CXCL-10: including E/A; E/e'lateral and E/e'septal, while E/e' positively correlated with CXCL-10. Diastolic dysfunction parameters also correlated with log sST2 levels, a negative correlation was seen with E/e'lateral and a positive correlation was seen with E/e'. Systolic dysfunction parameters positively correlated with hs-troponin: LVED, LVES, IVS, LVMASS and LVMASS index. In a multivariate analysis, sST2 and CXCL-10 were found to be significantly different in SLE vs. healthy controls, independent of each other and independent of cardiovascular risk factors. CONCLUSIONS: Soluble ST2 and CXCL-10 are markers of disease activity and accrued damage in SLE and may serve as sensitive biomarkers for detection of subclinical diastolic dysfunction, independent of traditional cardiovascular risk factors.

The Effect of Pregnancy on Disease Activity in Patients with Psoriatic Arthritis.

OBJECTIVE: To evaluate the effect of pregnancy on disease activity in psoriatic arthritis (PsA). METHODS: This is a retrospective case series. Review of the medical files of all female patients followed at the PsA clinic of 2 medical centers identified those with at least 1 pregnancy during followup and 1 visit during or soon after pregnancy. RESULTS: Twenty-five women with PsA (out of 107 women of reproductive age followed up in our PsA clinics) and 35 pregnancies were enrolled. Thirty-three pregnancies resulted in live healthy babies. In the whole group, there was no significant change in disease activity throughout pregnancy, while in 16 (48%) of pregnancies, patients worsened during the first postpartum year. In 15 out of 21 pregnancies, in which the women had been treated before conception with biologics, treatment was discontinued close to pregnancy or during the first trimester. Five of those 15 patients had been classified as having mild to severe PsA activity prior to pregnancy. That number increased to 8, 9, and 14 during the first and second trimesters and postpartum period, respectively. There was no significant change in degree of disease activity in 6 patients whose biologics were continued beyond the first trimester. Improvement in disease activity was observed during pregnancy among the nonbiologics-treated patients. Corticosteroids were initiated or the dosage was increased during 6 pregnancies, all involving patients whose biologics were stopped before pregnancy. CONCLUSION: Continuation of biologics therapy was associated with a low level of disease activity and a low probability of flare during pregnancy. Stopping treatment with biologics before pregnancy is associated with flare during pregnancy and the postpartum period.

Expression levels of selected genes can predict individual rheumatoid arthritis patient response to tumor necrosis factor alpha blocker treatment.

OBJECTIVES: Rheumatoid arthritis (RA) patients have many therapeutic options; however, tools to predict individual patient response are limited. The Genefron personal diagnostic kit, developed by analyzing large datasets, utilizes selected interferon stimulated gene expressions to predict treatment response. This study evaluates the kit's prediction accuracy of individual RA patients' response to tumor necrosis alpha (TNFα) blockers. METHODS: A retrospective analysis was performed on RA patients reported in published datasets. A prospective analysis assessed RA patients, before and 3 months after starting a TNFα blocker. Clinical response was evaluated according to EULAR response criteria. Blood samples were obtained before starting treatment and were analyzed utilizing the kit which measures expression levels of selected genes by quantitative real time polymerase chain reaction (PCR). ROC analysis was applied to the published datasets and the prospective data. RESULTS: The Genefron kit analysis of retrospective data predicted the response to a TNFα blocker in 53 of 61 RA patients (86.8% accuracy). In the prospective analysis, the kit predicted the response in 16 of 18 patients (89% accuracy) achieving a EULAR moderate response, and in 15 of 18 patients achieving a EULAR good response (83.3% accuracy). ROC analysis applied to the two published datasets yielded an AUC of 0.89. ROC analysis applied to the prospective data yielded an AUC of 0.83 (sensitivity - 100%, specificity - 75%) The statistical power obtained in the prospective study was .9. CONCLUSION: The diagnostic kit predicted the response to TNFα blockers in a high percentage of patients assessed retrospectively or prospectively. This personal kit may guide selection of a suitable biological drug for the individual RA patient.

Prevalence of Axial Spondyloarthritis Among Patients With Fibromyalgia: A Magnetic Resonance Imaging Study With Application of the Assessment of SpondyloArthritis International Society Classification Criteria.

OBJECTIVE: To evaluate the prevalence of sacroiliitis, the radiographic hallmark of inflammatory spondyloarthropathy, among patients diagnosed with fibromyalgia syndrome (FMS), using the current Assessment of SpondyloArthritis International Society (ASAS) criteria and magnetic resonance imaging. METHODS: Patients experiencing FMS (American College of Rheumatology 1990 criteria) were interviewed regarding the presence of spondyloarthritis (SpA) features and underwent HLA-B27 testing, C-reactive protein (CRP) level measurement, and magnetic resonance imaging examinations of the sacroiliac joints. FMS severity was assessed by the Fibromyalgia Impact Questionnaire and the Short Form 36 health survey. SpA severity was assessed by the Bath Ankylosing Spondylitis Disease Activity Index. RESULTS: Sacroiliitis was demonstrated among 8 patients (8.1%) and ASAS criteria for diagnosis of axial SpA were met in 10 patients (10.2%). Imaging changes suggestive of inflammatory involvement (e.g., erosions and subchondral sclerosis) were demonstrated in 15 patients (17%) and 22 patients (25%), respectively. The diagnosis of axial SpA was positively correlated with increased CRP level and with physical role limitation at recruitment. CONCLUSION: Imaging changes suggestive of axial SpA were common among patients with a diagnosis of FMS. These findings suggest that FMS may mask an underlying axial SpA, a diagnosis with important therapeutic implications. Physicians involved in the management of FMS should remain vigilant to the possibility of underlying inflammatory disorders and actively search for such comorbidities.

The Effect of the Presence of Fibromyalgia on Common Clinical Disease Activity Indices in Patients with Psoriatic Arthritis: A Cross-sectional Study.

OBJECTIVE: To study the effect of the presence of fibromyalgia (FM) on common clinical disease activity indices in patients with psoriatic arthritis (PsA). METHODS: Seventy-three consecutive outpatients with PsA (mean age 51.7 yrs; 42 females, 57.5%) were enrolled in a prospective cross-sectional study. FM was determined according to American College of Rheumatism criteria (2010 and 1990). All patients underwent clinical evaluation of disease activity and completed the Health Assessment Questionnaire (HAQ), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Dermatology Life Quality Index, and the Leeds Enthesitis Index (LEI). Disease activity was evaluated using the Composite Psoriatic Disease Activity Index (CPDAI), minimal disease activity (MDA), and the Disease Activity Index for Psoriatic Arthritis (DAPSA) scores. RESULTS: The overall prevalence of FM was 17.8% (13 patients), and all but 1 were women (12 patients, 92.3%, p = 0.005). CPDAI and DAPSA scores were significantly higher in patients with coexisting PsA and FM (9.23 ± 1.92 and 27.53 ± 19.23, respectively) than in patients with PsA only (4.25 ± 3.14 and 12.82 ± 12.71, respectively; p < 0.001 and p = 0.003). None of the patients with FM + PsA met the criteria for MDA, whereas 26 PsA-only patients did (43.3%, p = 0.003). HAQ, BASDAI, and LEI scores were significantly worse in patients with PsA and associated FM. CONCLUSION: Coexisting FM is related to worse scores on all tested measures in patients with PsA. Its influence should be taken into consideration in the treatment algorithm to avoid unnecessary upgrading of treatment.

Ultrasound assessment of enthesis thickening in psoriatic arthritis patients treated with adalimumab compared to methotrexate.

The objective of the study was to combine ultrasonographic (US) with clinical findings for comparing the effect of adalimumab (ADA) to methotrexate (MTX) on the thickness of tendons and enthesis in psoriatic arthritis (PsA) patients. Forty-three consecutive PsA patients were examined at baseline and after 6 and 12 weeks of treatment with ADA or MTX. The US assessment included thickness measurement of the extensor (ET) and flexor tendons (FT) of the second and third finger of both hands, plantar aponeurosis (PA) and the Achilles tendon (AT) bilaterally. Disease activity (DA) was assessed by the number of tender (TJ) and swollen joints (SJ), the number of inflamed enthesis (IE), pain assessment (PAI), and patient (PDAI) and physician (PHDAI) disease activity evaluations by visual activity score (VAS). Nineteen patients received MTX and 24 patients received ADA. All DA parameters improved in both groups. A decrease in thickness of tendons and enthesis was observed only in the ADA group, reaching a level of significance for the left AT (p = 0.01), left PA (p = 0.007), the second left FT (p = 0.04) and the third ET (p = 0.04). ADA patients showed a trend towards a better response to treatment compared to MTX patients that reach significance at week 6 of treatment for the thickness of left AT (p = 0.04), left PA (p = 0.03), the number of TJ (p = 0.0136), PAI (p = 0.0028), and PDAI (p = 0.029). ADA treatment for PsA compared to MTX significantly improved signs of DA and several US parameters. US assessment of enthesis can be an additional useful tool in the monitoring of psoriatic enthesopathy.

Efficacy and safety of vaccination against pandemic 2009 influenza A (H1N1) virus among patients with rheumatic diseases.

OBJECTIVE: To assess the efficacy and safety of vaccination against pandemic H1N1 virus in patients with rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), psoriatic arthritis (PsA), and ankylosing spondylitis (AS) compared with healthy controls. METHODS: The study population comprised 41 RA patients, 21 SLE patients, 17 PsA patients, 15 AS patients, and 25 healthy controls. All were vaccinated using the Novartis MF59-adjuvanted H1N1v monovalent influenza vaccine. The immunogenicity of the vaccine was assessed on day 1 and again 4 weeks later by hemagglutination inhibition assay. Geometric mean titers and seroconversion rates were calculated for each group. The safety of the vaccine was evaluated using the 28-joint Disease Activity Score (DAS28) for RA and PsA, the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), and the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI). RESULTS: The proportion of baseline protective levels of antibodies against H1N1 was similar in all but the AS group, in which it was lower. The geometric mean titers increased significantly in all 5 groups. A substantial proportion of patients and controls responded to the vaccine. The healthy controls demonstrated a better response than each of the other groups: 84% versus 56% for RA, 67% for SLE, 59% for PsA, and 53% for AS. Multivariate logistic regression analysis identified RA and PsA as parameters of significantly lower response. The DAS28, BASDAI, and SLEDAI remained unchanged after vaccination. CONCLUSION: Vaccination against pandemic H1N1 using an adjuvanted H1N1v monovalent influenza is safe and induced an appropriate response in patients with RA, SLE, PsA, and AS.

Large aorta and narrow arteries: two short stories of too long diagnostic delay.

The diagnosis of Takayasu arteritis requires a high degree of clinical suspicion. We herein present two cases of Takayasu arteritis that demonstrate two important aspects of the disease, which leaded to a significant delay in the diagnosis. The first case presented with an indolent disease with a clinical course of 20 years until clinical diagnosis was finally established while the second case shows the commonly unrecognised aspect of severe renovascular hypertension in these patients.

The increased proliferation of cultured neuroblastoma cells treated with vasoactive intestinal peptide is enhanced by simultaneous inhibition of neutral endopeptidase.

Vasoactive intestinal peptide (VIP) stimulates the neuroblastoma cell line (NMB) to proliferate. Neuropeptide activity can be inhibited by neutral endopeptidases that function intracellularly and in the extracellular milieu. NMB cells express neutral endopeptidase (NEP) activity that can be specifically inhibited by phosphoramidon (PA). Our data now show that phosphoramidon treatment increases the efficacy of VIP-stimulated neuroblastoma proliferation. These results suggest that membrane endopeptidases modulate VIP-associated cell proliferation and enhancement of endopeptidase activity may serve as a target for cancer therapy.