|Home | About | Journals | Submit | Contact Us | Français|
To answer three important questions related to the efficacy of daclizumab in multiple sclerosis (MS): 1. Is the therapeutic effect of daclizumab dependent on combination with IFN-β? 2. Is a higher dose of daclizumab more efficacious in patients with persistent disease activity? 3. Can biomarkers predict full- versus partial therapeutic response to daclizumab?
An open label baseline-versus-treatment phase II trial of daclizumab in MS patients with inadequate response to IFN-β. The 3 months of IFN-β baseline was followed by 5.5 months of combination therapy of IFN-β with daclizumab. If patients experienced at least a 75% reduction of contrast enhancing lesions (CEL) on brain MRI at month 5.5 as compared to baseline, daclizumab was continued as monotherapy for 10 months. Otherwise, the dose of daclizumab was doubled.
Neuroimmunology Branch (NIB) of the National Institute of Neurological Disorders and Stroke, Bethesda, Maryland.
15 MS patients receiving standard preparations of IFN-β, who experienced more than 1 relapse or sustained increase in disability in preceding 12 months, and had at least 2 CEL during 3 monthly baseline brain MRIs.
Daclizumab 1 mg/kg intravenous (IV) infusion every 4 weeks in combination with IFN-β (months 0 to 5.5) and as monotherapy (months 6.5–15.5).
The primary outcome was the reduction of CEL between IFN-β monotherapy, combination therapy and daclizumab monotherapy. The secondary outcomes included changes in clinical disability and immunological biomarkers.
Overall 33% of patients experienced some side effects of therapy. Two patients developed systemic side effects and daclizumab was discontinued. While daclizumab monotherapy was efficacious in nine out of thirteen MS patients, the combined daclizumab and IFN-β treatment was necessary to stabilize disease activity in four. Overall, daclizumab therapy led to 72% inhibition of CEL and to a significant improvement in clinical disability. Pilot biomarkers (expansion of CD56bright NK cells and contraction of CD8+ T cells) were identified that can differentiate between full- and partial daclizumab responders.
Daclizumab monotherapy is an effective treatment in the majority of patients with persistent disease activity on IFN-β therapy. Either combination of daclizumab with IFN-β or higher doses of daclizumab may be necessary to achieve optimal therapeutic response in all patients. Biomarkers may be able to identify patients with suboptimal response to daclizumab monotherapy. Only long-term administration to a large number of patients can fully define the safety and long-term efficacy of daclizumab as treatment for high-inflammatory MS.
Multiple Sclerosis (MS) is immune-mediated disorder of the brain and spinal cord, where at least part of the inflammatory process can be objectively measured by CEL on brain MRI. We1 and others2, 3 have previously demonstrated that daclizumab significantly inhibits CEL in MS, when used as an add-on therapy to IFN-β. We also reported an unexpected mechanism of action of daclizumab in MS, wherein the drug increases the number and function of immunoregulatory CD56bright NK cells, which downregulate adaptive T cell responses4. Although overall NK cell numbers and/or function has been described as diminished in patients with MS5, numbers of immunoregulatory CD56bright NK cells have not been systematically studied. We first identified expansion of these cells by daclizumab based on their combined phenotype as CD8αdim lymphocytes that are CD3neg/CD4neg/CD19neg 4. Recently, the diminished numbers of these CD8αdim cells were recognized by an unbiased large scale immunophenotyping approach as a distinguishing feature among MS, clinically isolated syndrome patients and control subjects6. Furthermore, CD56bright NK cells have now been shown to be expanded by several other effective immunomodulatory therapies in MS, such as IFN-β7 and rituximab8. These data suggest that CD56bright NK cells may be highly relevant immunoregulatory cells in MS. Since type-1 IFNs are known to enhance NK cell functions9, and conversely, because NK cells induce IFN-β during viral infection10, an important question emerged: Is there a synergism between IFN-β and daclizumab that is required for observed therapeutic efficacy in MS? Additionally, even though the 1mg/kg daclizumab IV every 4 weeks blocks more than 95% of CD25 on T cells in the blood4, it remained unclear whether CD25 saturation is also achieved in tissues and therefore, whether higher dose of daclizumab may be more efficacious. This article reports the MRI, clinical and immunological results of a second NIB open-label, baseline versus treatment phase II clinical trial of daclizumab in MS which addresses these new and important questions. Additionally it describes pilot biomarkers that potentially allow the early identification of patients who may not respond optimally to daclizumab monotherapy at the standard dose. Instead, these patients may need either a higher dose of daclizumab or combination with IFN-β to achieve full therapeutic benefit.
The trial design is schematically depicted in Figure 1. The trial was approved by the institutional review board. The inclusion criteria were: relapsing-remitting (RR-MS) or secondary-progressive (SP-MS) MS, age 18–65 years, Expanded Disability Status Scale (EDSS11) 1.0–6.5 and suboptimal response to IFN-β defined as: at least 1 MS exacerbation/year or progression of sustained disability by at least 1 EDSS step in the preceding 18 months. Presence of neutralizing antibodies to IFN-β was not assessed and did not represent an exclusion criterion. Patients with concurrent medical conditions that could influence the immune system or accumulation of disability were excluded. MS exacerbations were defined by Schumacher’s criteria12 and treated by IV methylprednisolone (IVMP; 1g/day ×5 days). MRI data collected within 28 days of IVMP were disregarded and substituted by data from the following month. 4/15 enrolled patients participated in a previously reported short-term NIH clinical trial of daclizumab plus IFN-β1.
In order to be enrolled, baseline MRI activity for each subject had to be at least 0.67 new CEL/month (Figure 1). Daclizumab 1mg/kg was administered as an IV infusion, initially 2 weeks apart for the first 2 doses, then every 4 weeks. After 7 doses of daclizumab (at month 5.5) the total number of CEL on the single scan was compared to the average number of CEL during baseline: when ≥75% of inhibition of CEL was observed, IFN-β therapy was slowly withdrawn (over 2–4 weeks). When less than 75% inhibition of CEL was observed at month 5.5, IFN-β therapy was continued and daclizumab dose was increased to 2mg/kg every 4 weeks. Numbers of CEL were analyzed monthly and if a sustained (>2 months) increase in CEL was noted during daclizumab monotherapy (above the average during combination therapy), IFN-β was reinstituted and patient continued on IFN-β and daclizumab combination therapy till the end of the trial. In an attempt to identify biomarkers that could predict full therapeutic response to daclizumab after withdrawal of IFN-β, we defined partial responders to daclizumab monotherapy as those patients who required combination of IFN-β with daclizumab, experienced MS relapse or had overall less than 50% decrease in CEL during daclizumab therapy.
The change in the average number of new and total CEL between baseline (IFN-β), combination therapy (IFN-β+daclizumab) and monotherapy (daclizumab) served as the primary outcome measure. Secondary outcomes included change in the volume of CEL, T2 lesion volume (T2LV), volume of T1 hypointensities (T1 lesion volume; T1LV), brain atrophy (Brain fractional volume; BFV) and change in clinical measures of disability: EDSS11 (from 0 = normal exam to 10 = death due to MS), Scripps Neurological Rating Scale13 (Scripps NRS; from 100 = normal exam to 0 = death due to MS) and MS functional composite14 (MSFC; calculated as z-score based on all collective baseline data in the cohort; higher numbers indicate an improvement in disability).
Whole blood samples were collected every 2–3 months and processed within 1 hour of collection: red blood cells were lysed by osmotic pressure and white blood cells were stained by a panel of commercially available antibodies and analyzed by flow cytometry as described4. Percentage of CD4+/CD3+ and CD8+/CD3+ T cells and CD56bright/CD3− and CD56dim/CD3− NK cells were calculated for each time-point. Absolute numbers of these cellular subpopulations were derived from the absolute lymphocyte count provided by the NIH Clinical Center laboratory from identical sample collections.
MRIs were acquired at 1.5 T using a standard protocol1. CEL were recorded on hard copy films by consensus of two radiologists. All volumetric analyses were performed by a single experienced rater using semiautomated thresholding techniques (PV-WAVE15 and MEDx) as described1.
Statistical differences between treatment periods were based on Friedman Repeated Measures Analysis of Variance on Ranks with the predetermined P value < 0.05, using Student-Newman-Keuls procedure to correct for multiple comparisons. Differences between full and partial responders were based on Mann-Whitney Rank Sum Test.
The patient population is described in Table 1.
Two patients did not complete the trial because of side-effects possibly related to daclizumab monotherapy (Table 1). Both patients (MS-Z2-05 and MS-Z2-13) developed systemic immune responses 1–2 months after withdrawal of IFN-β, characterized by mouth ulcers, photosensitivity rash and transient formation of autoantibodies that required corticosteroid therapy for resolution. Two other patients developed adverse events that required transient cessation of daclizumab due to lymphopenia (MS-Z2-06) and generalized lymphadenopathy (MS-Z2-07). However, both of these patients were re-dosed with excellent outcomes.
Only one patient (MS-Z2-11) did not reach the interim end-point of a decrease in CEL by 75% at month 5.5 and was put on a double dose of daclizumab + IFN-β with a subsequent excellent therapeutic response. In fourteen patients the IFN-β was withdrawn after 5.5 months, but in 3 patients it was restarted due to sustained re-appearance of CEL. Trial results (intention to treat analysis on all 15 subjects) are depicted in Figure 2. We observed 72% inhibition of new (P=0.002) and 77% inhibition of total CEL (P<0.001) by daclizumab. This inhibition of CEL developed gradually and continued during dosing, so that a decrease in the volume of CEL reached statistical significance (P<0.001) even when comparing combination therapy and monotherapy periods (Figure 2A). We observed improvements in all clinical measures of disability (Figure 2B; for EDSS P<0.001, for Scripps NRS P<0.001 and for MSFC P=0.002). There were no significant changes in T2LV (P=0.424) while both T1LV (P=0.023) and BFV (P=0.009) increased transiently between baseline and combination therapy but stabilized between combination therapy and monotherapy (Figure 2C). The whole brain magnetization transfer ratios (MTR; average/median) did not change significantly (P=0.558) from baseline (0.334/ 0.340) to combination therapy (0.335/ 0.337) and monotherapy (0.336/ 0.339).
We reported that daclizumab therapy expands CD56bright NK cells and that this expansion correlates with the contraction in absolute numbers of peripheral CD4+ and CD8+ T cells4. This trial allowed us to answer the question whether this effect is related to IFN-β therapy. We observed further expansion of CD56bright NK cells (P<0.001) and concomitant contraction of CD4+ (P=0.008) and CD8+ T cell (P=0.002) absolute numbers during daclizumab monotherapy in comparison to IFN-β+daclizumab combination therapy (Figure 3A). Based on our previous observation that CD56bright NK cells regulate T cell responses4, we assessed the ratios between CD56bright NK cells and effector lymphocyte subsets (Figure 3B), which also further declined during daclizumab monotherapy (P<0.001 for both CD4/CD56bright NK and CD8/CD56bright NK cell ratios). Seven patients fulfilled partial responder criteria (see methods and Table 1). When analyzing immunological differences between full and partial responders, we observed that the former had at least a 10% decrease in absolute numbers of CD8+ T cells and CD4+ T cells and at least a 300% increase in CD56bright NK cells during combination therapy as compared to baseline (Figure 3C). Partial responders showed either an increase, or less than 10% decrease in CD4+ and CD8+ T cell numbers and less than 300% increase in CD56bright NK cells. While full responders further increased the percentage of CD56bright NK cells (and CD8αdim/CD3neg lymphocytes) during daclizumab monotherapy to more than 400% of baseline, partial responders experienced significantly smaller expansion of these regulatory cells (Figure 3C, last panel).
Our data demonstrate that while daclizumab monotherapy is effective for the majority of MS patients with persistent MRI and clinical activity while receiving IFN-β therapy, there is an additive effect of daclizumab and IFN-β, which may be advantageous for those MS patients that are most-difficult to treat. In comparison to a previously reported study by Rose et al.3, which was performed in parallel to our first daclizumab study, the present trial provides important additional information: 1. In addition to EDSS and NRS clinical scores, which need to be interpreted with caution in an open label trial due to their high rater-dependency, we provide data on MSFC, which is based on objectively quantifiable measures. Hence, the continuous improvement of MSFC even between combination therapy and monotherapy is encouraging. While learning effect may influence MSFC scores when tested infrequently, all three components of MSFC were tested monthly in our trial, making it unlikely that learning could have affected the results after more than 10 months of testing. 2. In addition to CEL analysis, our study provides evaluation of volumetric MRI measures, including MTR. Whereas the improvement in disability measures suggests the possibility that daclizumab enhances repair, we consider this unlikely in view of its apparent lack of effect on T1LV and BFV. Nevertheless, these MRI measures are susceptible to depicting edema associated with inflammation, which makes them less sensitive markers for tissue destruction in short-term clinical trials in MS16. However, neither did we observe any improvement in whole brain MTR, even though this too may be a measure that is insensitive to depict focal, lesion-related repair. 3. Our immunological data, demonstrating further increase in CD56bright NK cells and additional decline in CD4+ and CD8+ T cell numbers after cessation of IFN-β therapy indicates that both drugs have distinct immunological mechanisms of action and therefore their combination is more effective than either drug alone. 4. Although we treated only one patient with higher dose of daclizumab (2mg/kg), the remarkable efficacy of this dose (complete elimination of CEL in this patient for subsequent 10 months) suggests that higher doses of daclizumab deserve further study as an alternative to daclizumab/IFN-β combination therapy. The fact that we observed >95% saturation of CD25 with daclizumab on peripheral blood lymphocytes in all patients, irrespective of their response status (data not shown), led us to believe that higher doses of daclizumab may be necessary to fully saturate CD25 in tissues. 5. Finally, it would be of great benefit to have biomarkers that allow prediction of treatment responsiveness. Our study indicates that the extent of changes in CD8+ T cell and CD56bright NK cell counts induced by daclizumab within first 2–4 months of therapy may be able to identify those patients who are unlikely to have full therapeutic response upon withdrawal of IFN-β. These biomarkers have to be considered as preliminary, but deserve validation in large phase II/III trials of daclizumab. The fact that we could demonstrate statistically significant differences between full and partial responders even in such small cohort, using non-parametric statistics, is nevertheless encouraging.
Therapeutic efficacy of daclizumab in inhibiting brain inflammation in MS has been now confirmed by several trials, including a recently reported randomized double blind Phase II trial of daclizumab plus IFN-β combination therapy (Choice study)17. This trial examined efficacy of subcutaneous formulation of two doses of daclizumab (1mg/kg and 2mg/kg) administered every two weeks against placebo. The study patients who received higher dose showed a statistically significant 72% reduction in the number of new or enlarged CEL at week 24, compared to patients on interferon beta therapy alone. Other Phase II trials, including those testing efficacy of daclizumab monotherapy are currently ongoing17. However, daclizumab has to undergo vigorous testing in Phase III double-blinded clinical trials before it can be accepted as a safe and effective MS therapy.
Disclosure: Co-authors B.B., T.A.W., H.M and R.M. are co-inventors on NIH patents related to the use of daclizumab in MS and as such received royalty payments. The research was supported by the Intramural research program of the National Institute of Neurological Disorders and Stroke, NIH.