Secondary Therapy Failure Research Articles

Botulinum toxin antibody titres: measurement, interpretation, and practical recommendations

Botulinum toxin (BT) therapy may be blocked by antibodies (BT-AB) resulting in BT-AB induced therapy failure (ABF). BT-AB may be detected by the mouse lethality assay (MLA), the mouse diaphragm assay (MDA) and the sternocleidomastoid test (SCMT). For the first time, we wanted to compare all three BT-AB tests and correlate them to subjective complaint of complete or partial secondary therapy failure in 37 patients with cervical dystonia (25 females, 12 males, age 51.2 ± 11.4 years, disease duration 12.4 ± 6.3 years). Complaint of therapy failure was not correlated with any of the BT-AB tests. MDA and MLA are closely correlated, indicating that the MDA might replace the MLA as the current gold standard for BT-AB measurement. The SCMT is closely correlated with MDA and MLA confirming that BT-AB titres and BT's paretic effect are in a functional balance: low BT-AB titres are reducing BT's paretic effect only marginally, whereas high BT-AB titres may completely block it. When therapy failure is classified as secondary and permanent, BT-AB evaluation is recommended and any BT-AB test may be applied. For MDA > 10 mU/ml, MLA > 3 and SCMT < 25%, ABF is highly likely. MDA < 0.6 mU/ml are therapeutically irrelevant. They are neither correlated with pathologic MLA nor with pathologic SCMT. They should not be the basis for treatment decisions, such as switching dystonia therapy to deep brain stimulation. All other results are intermediate results. Their interactions with therapy efficacy is unpredictable. In these cases, BT-AB tests should be repeated or one or two additional test methods should be applied.

The prognostic value of serological titres for clinical outcomes during treatment and follow-up of patients with chronic Q fever

ObjectivesWe assessed the prognostic value of phase I IgG titres during treatment and follow-up of chronic Q fever. MethodsWe performed a retrospective cohort study to analyse the course of phase I IgG titres in chronic Q fever. We used a multivariable time-varying Cox regression to assess our primary (first disease-related event) and secondary (therapy failure) outcomes. In a second analysis, we evaluated serological characteristics after 1 year of therapy (fourfold decrease in phase I IgG titre, absence of phase II IgM and reaching phase I IgG titre of ≤1:1024) with multivariable Cox regression. ResultsIn total, 337 patients that were treated for proven (n = 284, 84.3%) or probable (n = 53, 15.7%) chronic Q fever were included. Complications occurred in 190 (56.4%), disease-related mortality in 71 (21.1%) and therapy failure in 142 (42.1%) patients. The course of phase I IgG titres was not associated with first disease-related event (HR 1.00, 95% CI 0.86–1.15) or therapy failure (HR 1.02, 95% CI 0.91–1.15). Similar results were found for the serological characteristics for the primary (HR 0.97, 95% CI 0.62–1.51; HR 1.12, 95% CI 0.66–1.90; HR 0.99, 95% CI 0.57–1.69, respectively) and secondary outcomes (HR 0.86, 95% CI 0.57–1.29; HR 1.37, 95% CI 0.86–2.18; HR 0.80, 95% CI 0.48–1.34, respectively). DiscussionCoxiella burnetii serology does not reliably predict disease-related events or therapy failure during treatment and follow-up of chronic Q fever. Alternative markers for disease management are needed, but, for now, management should be based on clinical factors, PCR results, and imaging results.

Clinical Improvement After Treatment With IncobotulinumtoxinA (XEOMIN®) in Patients With Cervical Dystonia Resistant to Botulinum Toxin Preparations Containing Complexing Proteins.

This study investigated the clinical long-term effect of incobotulinumtoxinA (incoBoNT/A) in 33 cervical dystonia (CD) patients who had developed partial secondary therapy failure (PSTF) under previous long-term botulinum toxin (BoNT) treatment. Patients were treated four times every 12 weeks with incoBoNT/A injections. Physicians assessed treatment efficacy using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) at the baseline visit, week 12 and 48. Patients rated quality of life of CD with the Craniocervical Dystonia Questionnaire (CDQ-24). Titres of neutralizing antibodies(NAB) were determined at start of the study and after 48 weeks. All patients had experienced significant and progressive worsening of symptoms in the last 6 months of previous BoNT treatment. Repeated incoBoNT/A injections resulted in a significant reduction in mean TWSTRS at week 12 and 48. Patients' rating of quality of life was highly correlated with TWSTRS but did not change significantly over 48 weeks. During the 48 weeks -period of incoBoNT/A treatment NAB titres decreased in 32.2%, did not change in 45.2%, and only increased in 22.6% of the patients. Thus, repeated treatment with the low dose of 200 MU incoBoNT/A over 48 weeks provided a beneficial clinical long-term effect in PSTF and did not booster titres of NAB.

The role of human serum albumin and neurotoxin associated proteins in the formulation of BoNT/A products

Botulinum neurotoxin (BoNT) is synthesized as a progenitor toxin complex (PTC) by Clostridium botulinum. This PTC comprises, in addition to the neurotoxin itself, neurotoxin associated proteins (NAPs) which are composed of three hemagglutinins and one non-toxic, non-hemagglutinin protein. After oral ingestion, these NAPs protect the neurotoxin from the low pH and proteases in the gastrointestinal tract and play a role in the entry via the intestinal barrier. Two of the three therapeutically used botulinum neurotoxin serotype A (BoNT/A) products (onabotulinumtoxinA and abobotulinumtoxinA) contain different amounts of NAPs, while incobotulinumtoxinA, lacks these proteins. In addition, human serum albumin (HSA) that is supposed to stabilize BoNT/A is added at different concentrations. Up to now, the function of the NAPs and HSA after parenteral therapeutic application is not completely understood.To investigate the influence of NAPs and HSA on potency of BoNT/A, we used the ex vivo mouse phrenic nerve hemidiaphragm assay.Increasing doses of HSA resulted dose-dependently in a more pronounced effect of BoNT/A. Though, a plateau was reached with concentrations of 0.8 mg/ml HSA and higher, the accessory addition of NAPs in a relevant amount (4 ng/ml) did not further enhance the effect of BoNT/A.In conclusion, in our ex vivo assay an adequate concentration of HSA prevented BoNT/A from loss of effect and supplementary NAPs did not alter this effect. A confirmation of these data in an in vivo assay is still lacking. However, it might be supposed that even in clinically applied BoNT/A products an increase of HSA accompanied by the avoidance of NAPs could potentially reduce the injected dose and, thus, the risk of unwanted side effects, the treatment costs as well as the risk of a secondary therapy failure due to BoNT/A neutralizing antibodies.

Antibody-Induced Failure of Botulinum Toxin A Therapy in Cosmetic Indications

Botulinum toxin (BT) is a safe and effective treatment for cosmetic indications. Formation of BT antibodies can occur but has previously been reported in cosmetic indications in two cases only. To report another four patients with this phenomenon. Two patients received abobotulinumtoxinA; one received the current formulation of onabotulinumtoxinA and one both abobotulinumtoxinA and onabotulinumtoxinA. Complete secondary therapy failure (CSTF) occurred after 3-, 5-, 10-, and 13-injection series; cumulative treatment times of 18, 16, 25, and 65 months; and cumulative doses of 240 MU onabotulinumtoxinA, 245 MU abobotulinumtoxinA, 1,180 MU abobotulinumtoxinA, and 120 MU onabotulinumtoxinA/270 MU abobotulinumtoxinA, respectively. Average interinjection intervals were 87, 273, 150, and 119 days, and average single doses were 80 MU onabotulinumtoxinA, 68 MU abobotulinumtoxinA, 82 MU abobotulinumtoxinA, and 30 MU abobotulinumtoxinA/30 MU onabotulinumtoxinA. Risk factors for CSTF included booster injections (2 patients) and increased immune system reagibility (1 patient). BT antibody titers were 2.7, 7.0, and more than 10.0 mU/mL on the mouse diaphragm assay. CSTF can occur after cosmetic BT injections in patients with high immune system reagibility and in patients receiving booster injections, but also in unremarkable patients with typical treatment parameters. Its incidence is unknown. Recommended treatment parameters may reduce the risk of CSTF, but may not eliminate it.

Hemifacial spasm and reinnervation synkinesias: long-term treatment with either Botox® or Dysport®

Botulinum toxin is considered the treatment of choice for hemifacial spasm (HFS) and reinnervation synkinesias (RS). We present 133 patients with HFS (n = 97) and RS (n = 36) who have been treated with either Botox (n = 78) or Dysport (n = 55) exclusively for 6 years (range 2-12 years). The Botox dose was 21 +/- 8 MU, the Dysport dose 46 +/- 22 MU. The therapeutic effect started after 7.1 +/- 2.3 days and lasted for 12.5 +/- 3.9 weeks. It was stable throughout the observation period in 85% of all patients. Adverse effects occurred in 5.4% of injection series. No patient terminated treatment because of unsatisfactory results. Secondary therapy failure did not occur. With an effective conversion ratio of Botox:Dysport = 1:2.56 there were no differences between both drugs with respect to therapeutic efficacy and adverse effects thus confirming the hypothesis that there may not be intrinsic differences between both products.

Routine use of Xeomin® in patients previously treated with Botox®: long term results

Based upon large and carefully performed studies Xeomin was first registered in 2005. However, its real potential can only be assessed, when it is used outside of study design restrictions, in an independent setting, in off-label indications and during continued use. Two hundred and sixty-three patients (91 with dystonia, 84 with spasticity, 17 with hemifacial spasm and re-innervation synkinesias, 64 with hyperhidrosis, 7 with hypersalivation), who were previously treated with Botox for at least 1 year under stable conditions, were converted in a blinded fashion to Xeomin using a 1:1 conversion ratio and identical treatment parameters. Therapeutic outcome and adverse effects were monitored by neurological examination and structuralised interviews. In 223 patients (all except those with axillary hyperhidrosis) Xeomin was used continuously throughout a 3 year period. Altogether 1050 injection series were performed. Patients with dystonia received 261.5 +/- 141.0 MU Botox/Xeomin, patients with spasticity 450.5 +/- 177.1 MU, patients with hemifacial spasm and reinnervation synkinesias 44.7 +/- 19.5 MU and patients with hyperhidrosis 286.9 +/- 141.6 MU. The maximum botulinum toxin dose applied was 840 MU. There were no subjective or objective differences between Botox and Xeomin treatments with respect to onset latency, maximum and duration of their therapeutic effects and their adverse effect profiles. Long-term use did not reveal additional safety relevant aspects. None of the patients lost therapeutic efficacy during the observation period. Xeomin can be used safely in doses of up to 840 MU. Even when applied in high doses it did not produce secondary therapy failure. There were no diffusion differences between Botox and Xeomin. Using a conversion ratio of 1:1 Xeomin and Botox can easily be exchanged in a continued treatment.

Neutralizing Antibodies and Secondary Therapy Failure After Treatment With Botulinum Toxin Type A

As the indications and duration of treatment of botulinum toxin type A (BoNT-A) increase, so do reports of patients who fail therapy after initially responding well. Although a loss of efficacy is commonly thought to be associated with neutralizing antibodies (NAbs), this relationship is not strongly correlated, and other factors may play a significant role. To explore this issue, we evaluated levels of NAbs in a large selected cohort of secondary nonresponders to BoNT-A using the highly sensitive mouse phrenic nerve-hemidiaphragm assay. Serum samples from 503 patients treated with BoNT-A who had a variety of diagnoses were tested for the presence of NAbs. Fewer than half of the patients (n = 224, 44.5%) were found to be NAb-positive, indicating that in more than half of the secondary nonresponders, lack of efficacy is not due to NAb formation. The proportion of secondary nonresponders with NAbs was greater for higher dose indications (focal spasticity and spasmodic torticollis) than for lower dose indications (blepharospasm and hemifacial spasm) and increased with shorter injection intervals. Neutralizing antibody development was independent of the commercial preparation used. Our results indicate that although NAb formation does play a role in secondary treatment failure with BoNT-A, this is not the cause in all patients, and the influence of other factors needs to be investigated. Gaining a better understanding of the underlying mechanisms for secondary treatment failure may help in the prediction, diagnosis, management, and prevention of this problem.

Editorial Comment

In therapy with botulinum toxin type A (BoNT/A), antibodies against BoNT/A (BoNT/A-AB) may be a reason for a complete secondary therapy failure.1 Currently, approximately 5% of patients with cervical dystonia that are receiving repeated BoNT/A injections have complete secondary therapy failure due to BoNT/A-AB.2 This manuscript is interesting and the first paper to investigate BoNT/A-AB in patients receiving BoNT/A injections at the lower urinary tract.3 The study demonstrates that the incidence of BoNT/AB was 16% after treatment and there was no correlation between the presence of BoNT/A-AB and the total number of previous injections. It is unclear why the prevalence of BoNT/A-AB was much higher in bladder injections than that in other fields. On these points this study is very interesting; however, there are some shortcomings. This study clearly demonstrated that BoNT/A-AB can develop after injections to the lower urinary tract. However, the results of this study cannot conclude that antibodies will cause therapeutic failure. Objective success was noted in seven patients, in whom one had antibodies (14%); and objective failure was noted in 11 patients, in whom three had antibodies (27%). It is difficult to conclude that BoNT/A-AB has a direct association with therapeutic failure in this study. In neurology, re-injection at too short intervals contributes to BoNT/A resistance. Therefore, they recommended ‘drug holiday’ to prevent BoNT/A-AB.4 What should we do if patients become clinically non-responsive to BoNT/A? Botulinum toxin type B might be effective to such patients.5 In the future, application of a new BoNT/A preparation with low antigenic potency might be a promising treatment option.6

Neutralizing antibodies in dystonic patients who still respond well to botulinum toxin type A

Complete secondary therapy failure due to antibodies against botulinum toxin A (BoNT/A-ABs) may raise extensive treatment difficulties. We tested whether neutralizing BoNT/A-ABs can be detected in dystonic patients with good clinical responses to botulinum toxin A (BoNT/A) treatment. We used the ninhydrin sweat test (NST) and the mouse diaphragm test (MDT) in 28 subjects. Of 119 dystonic patients who responded well to BoNT/A, we randomly selected 14 and compared the results of the NST and MDT with 14 healthy controls. Higher BoNT/A-AB titers correlated significantly with smaller anhidrotic areas. We found seven patients with borderline antibody (AB) values (MDT 0.4 to 0.8 mU/mL) with significantly smaller anhidrotic areas (NST) compared with healthy controls and AB-negative patients. Risk factors for smaller anhidrotic areas were short injection intervals but not prolonged exposure to BoNT/A or high injection doses. These data demonstrate that >40% of dystonic patients who respond well to botulinum toxin A (BoNT/A) show partial nonresponsiveness on the ninhydrin sweat test and have low titers of neutralizing BoNT/A antibodies.

Clinical use of non-a botulinum toxins: botulinum toxin type B

Botulinum neurotoxin type B (BT, BT-B) has been used as NeuroBloc/MyoBloc since 1999 for treatment of cervical dystonia, hyperhidrosis, spastic conditions, cerebral palsy, hemifacial spasm, bladder dysfunction, spasmodic dysphonia, sialorrhoea, anal fissures, piriformis syndrome, various pain conditions and cosmetic applications. Generally, its therapeutic effects are comparable to BT type A (BT-A). The adverse effect profiles of BT-B and BT-A, however, differ considerably. BT-B has been found to produce more regional as well as systemic anticholinergic adverse effects, such as dryness of mouth, accommodation difficulties, conjunctival irritation, reduced sweating, dysphagia, heartburn, constipation, bladder voiding difficulties and dryness of nasal mucosa. In BT-B the relationship between autonomic and motor effects known from BT-A is substantially shifted towards autonomic effects. BT-B, therefore, should be used carefully in patients with autonomic disorders and in patients with concomitant anticholinergic therapy. If NeuroBloc/MyoBloc is used to treat cervical dystonia patients with antibody-induced failure of BT-A therapy, 86% of those will develop complete secondary therapy failure after five applications. If NeuroBloc/MyoBloc used to treat cervical dystonia patients without prior exposure to BT, 44% of those will develop complete secondary therapy failure after nine applications. NeuroBloc/MyoBloc, therefore, is associated with substantial antigenicity problems originating from a particular low specific biological potency. Systemic anticholinergic adverse effects and high antigenicity limits the clinical use of NeuroBloc/MyoBloc considerably.

Mouse diaphragm assay for detection of antibodies against botulinum toxin type B

With the advent of a commercial preparation of botulinum toxin type B (BT-B) for treatment of cervical dystonia detection of antibodies against BT-B (BT-B-AB) becomes necessary. For this purpose, we carried out a mouse diaphragm assay (MDA) by continuous measurement of the twitch force of a mouse hemidiaphragm preparation elicited by electric stimulation of its phrenic nerve. After exposing the preparation to BT-B 3 ng/ml the time to half-maximal twitch force reduction (paralysis time [PT]) was 69 +/- 4 min (n = 25). Addition of sera from patients with antibodies against BT-A produced a PT of 68 +/- 5 min (n = 24), whereas addition of sera from controls with antibodies against tetanus toxoid produced a PT of 67 +/- 6 min (n = 30). When defined amounts of BT-B-AB were added to the MDA, PT was prolonged. This prolongation was correlated closely to the amount of BT-B-AB added, thus producing a calibration curve. The threshold for BT-B-AB detection was 0.4 mU/ml. When sera from 7 patients (4 women, 3 men; age 50.6 +/- 14.2 years) with cervical dystonia (Toronto Western Spasmodic Torticollis Rating Scale score, 18.9 +/- 2.9) and complete secondary failure of BT-B therapy (NeuroBloc; Elan Pharmaceuticals, Shannon, Ireland; 12,229 +/- 2,601 MU/injection series, 1.86 +/- 0.69 injection series before complete secondary therapy failure; 100.4 +/- 15.8 days between injection series with normal therapeutic effect) were tested, BT-B-AB titers of more than 10 mU/ml were found in all of them. The MDA can be used to measure neutralizing BT-B-AB titers quantitatively and with adequate sensitivity and specificity. Further studies are necessary to understand the role of intermediate BT-B-AB titers in partial BT-B therapy failure.

Clinical presentation and management of antibody-induced failure of botulinum toxin therapy.

Therapy with botulinum toxin (BT) can fail due to numerous reasons, including failure due to formation of antibodies against BT (BT-AB, AB-TF). AB-TF is a secondary therapy failure, i.e. it occurs during the course of an ongoing BT therapy. It can be subjective or objective, temporary or permanent, and partial or complete. Complete AB-TF is usually preceded by injection series with partial AB-TF in which the therapeutic effect is reduced in its intensity and duration. AB-TF usually occurs within 2 or 3 years after initiation of BT therapy. After 4 years it is rare. BT-AB are neutralising or blocking by definition, i.e. they are directly interfering with BT's biological mechanism of action. Non-neutralizing or non-blocking antibodies occur. BT-AB can be detected by the mouse diaphragm assay, the mouse protection assay, and by patient-based tests such as the sternocleidomastoid test, the extensor digitorum brevis test, and the frowning test. Enzyme-linked immunosorbent assays (ELISA) have a low specificity and a low sensitivity for detection of BT-AB. BT-AB titres drop spontaneously after cessation of BT therapy but latencies are too long to be compatible with an effective BT therapy. BT dosage increase can be successful to overcome AB-TF when AB-TF is partial and when BT-AB titres are low. Usage of alternative BT type A preparations fail to overcome AB-TF. Alternative BT types, such as BT type B and BT type F, are initially successful in AB-TF, but stimulate formation of antibodies against the alternative BT types after few applications. BT-AB reduction with immunosuppressants and inactivation of BT-AB by intravenous immunoglobuline application has not yet been achieved. Extraction of BT-AB by plasmapheresis and immunoadsorption is possible but is associated with substantial logistic problems. Prevention of BT-AB formation, therefore, is of paramount importance. Identified risk factors for BT-AB formation must be taken into account when BT therapy is planned. The most interesting perspective seems to be the development of new BT preparations with reduced antigenicity.

Botulinum toxin antibody type A titres after cessation of botulinum toxin therapy.

In some patients, therapy with botulinum toxin type A (BT-A) becomes ineffective due to formation of antibodies (BT-A-AB). The time course of BT-A-AB titres after cessation of BT-A therapy was quantitatively studied to determine whether and when they might drop. Thirteen patients (eight women, five men) with various dystonic syndromes and complete secondary therapy failure (CSTF) were included in this study (age at initiation of BT-A therapy, 48.2 +/- 11.3 years; number of injection series, 7.7 +/- 2.9; treatment time, 678.8 +/- 385.6 days; mean interinjection interval, 90.4 +/- 35.5 days; mean single dose, 546.7 +/- 336.9 EMU; cumulative dose, 4185.1 +/- 3375.7 EMU [1 EMU = 1 botox MU = 3 dysport MU]). During a monitoring period of at least 750 days after occurrence of CSTF, two or more BT-A-AB tests using the quantitative mouse diaphragm assay were performed. Eight of 13 BT-A-AB titres decreased. The onset of decrease could be detected after between approximately 500 and 1,750 days. After 1,250 to 2,250 days they had dropped below a level of 0.002 U/ml, where CSTF is unlikely. Five of 13 BT-A-AB titres did not decrease. For three of these five, the monitoring period was less than 1,500 days; a chance to drop remained. The other two were monitored for up to 2,400 days. Patients with decreasing and nondecreasing BT-A-AB titres did not exhibit statistically significant differences in either clinical characteristics or treatment parameters. When BT-A therapy was stopped the majority of BT-A-AB titres eventually decreased, allowing reinitiation of BT-A therapy. Application of new BT-A preparations with low antigenic potency might then become an interesting treatment option.