Abstract:
Progressive multifocal leukoencephalopathy (PML) has been identified in patients taking natalizumab (NMAB) for the treatment of multiple sclerosis (MS). This patent application provides a novel method of patient screening and monitoring intended to decrease the risk of PML and other opportunistic central nervous system (CNS) diseases in patients undergoing MS therapy with NMAB, and proposes a novel method of screening and monitoring intended to decrease the risk of opportunistic disease processes of the CNS during the treatment of other medical disorders with NMAB.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Natalizumab (NMAB) is a humanized antibody that binds to surface-expressed integrins on all leukocytes except neutrophils, and inhibits adhesion molecules on these leukocytes from binding to their counter-receptors. In so doing, NMAB disrupts the transmigration of these leukocytes across endothelial tissue and into inflamed parenchymal tissue. NMAB additionally inhibits recruitment and inflammatory activity of activated immune cells. Although the exact mechanism of action of NMAB is unclear, it is thought that at least part of the therapeutic benefit of NMAB in the treatment of MS is due to NMAB&#39;s ability to decrease the number of activated inflammatory cells, including T-lymphocytes, across the blood-brain barrier (BBB), thus decreasing the degree of inflammation within the CNS. 
         [0002]    MS is considered to be a chronic inflammatory disease of the CNS, which is often due to myelin sheath and axonal CNS damage secondary to an autoimmune inflammatory process that usually includes a T-cell response. A more virus or toxin related demyelination has also been identified as a primary disorder within oligodendrocytes. In double blind, multi-center, placebo controlled trials, a therapeutic benefit of NMAB has been observed in patients with MS; and this is, at least in part, attributed to decreasing the extent of T-lymphocyte entry across the BBB and into the CNS, and therefore decreasing pathologic inflammatory disease within the CNS. 
         [0003]    Unfortunately, in 2005 it was observed that three patients who had been treated with NMAB were diagnosed with Progressive Multi-focal Leukoencephalopathy (PML), a rare and often fatal disease of the brain that has been observed historically in immunosuppressed patients. While it is not definitively clear at the time of this application whether or not the diagnosed PML was caused by treatment with NMAB or simply associated with same, the inventors&#39; understanding of the etiology of PML leads them to believe that the former is more likely. PML is progressive (over time it continues to encroach more and more brain tissue), multi-focal (occurs in more than one location within the brain), and is a disease of the white matter of the brain (leukoencephalopathy). Like MS, PML causes demyelination and can result in severe and often fatal neurological injury. The etiology of PML is understood to originate from a virus, the JC Virus, which can infect and kill oligodendrocytes, which are specialized neural cells that produce the myelin essential for proper neuronal function. 
         [0004]    While still rare, the resurgence of PML during the past two decades was in part due to the compromised T-cell mediated immunity associated with patients with AIDS. In short, treatment with NMAB results in a CNS immunosuppression of sorts, akin (at least form the point of view of the CNS) to the more ubiquitous T-cell immunosuppression observed in patients with AIDS. It has also been observed that there is an association between JC Virus-specific cytotoxic T lymphocytes (CTL) and the early control of PML. That is, the more JC Virus-specific CTL, the more favorable outcome in patients with PML. 
         [0005]    Although far from universal, prolonged PML survival after Highly Active Antiretroviral Therapy (HAART) (against the AIDS virus) has been reported and prolonged survival has been observed with JC Viral clearance from the CSF. 
     
    
     DESCRIPTION OF THE INVENTION 
       [0006]    The invention relates in part to an appreciation that should PML or another opportunistic CNS disease occur as a result of CNS immunosuppression secondary to NMAB therapy, then the sooner NMAB therapy is discontinued, the more likely a patient will minimize CNS damage due to a CNS opportunistic disease, and the more likely that that same patient will recover. Because MS can be such a devastating disease, because treatment options for MS (and other medical disorders that may potentially benefit from NMAB therapy) are relatively limited, because NMAB has shown significant clinical benefit to MS patients in proper clinical studies, and because all medications carry risk and are assessed by their risk to benefit ratio, it may not be necessary to permanently remove NMAB as a therapeutic option for patients. Rather, it may be possible to create a means of managing the risk associated with NMAB, and in particular to produce a method of screening and monitoring patients undergoing NMAB therapy to minimize the risk of opportunistic CNS disease that may occur secondary to CNS immunosuppression. 
         [0007]    The invention provides methods to address not only the risk of PML in patients treated with NMAB, but to also address other opportunistic diseases of the CNS that may result from a compromised CNS T-cell immune response due to treatment with NMAB. Diseases of the CNS that may occur as a result of CNS T-cell mediated immunosuppression include but are not limited to PML (secondary to the JC Virus), cytomegalovirus (CMV) infection, toxoplasmosis, cryptococcosis,  tuberculosis  (TB) and primary CNS lymphoma (PCL) which is almost always due to Epstein-Barr Virus (EBV). 
       PREFERRED MODES OF PRACTICING THE INVENTION 
     Prior To Beginning Treatment With NMAB A Baseline Screening Evaluation Should Be Undertaken 
       [0008]    Prior to beginning treatment with NMAB and prior to CSF assessment, a patient should first be required to have an MRI brain imaging study, which will also serve as a baseline study with which to compare future MRI brain images. 
         [0009]    Prior to the initiation of NMAB therapy, cerebrospinal fluid (CSF) from the intended patient should be tested by polymerase chain reaction (PCR) (or other diagnostic assay if it is more sensitive) to detect the presence of one or more of CMV, JC Virus, Toxoplasma gondii, EBV, Cryptococcus neoformans, and TB. 
         [0010]    Prior to beginning treatment with NMAB, a patient should also be required to have an ophthalmologic examination to establish and document a baseline retinal status and to rule out the presence of ocular CMV (the optic nerve is a component of the CNS and may be observed in part by a simple ocular examination). 
         [0011]    The presence of a positive CSF PCR (or other more specific diagnostic test) for CMV, EBV, TB, JC Virus, Toxoplasma gondii, or Cryptococcus neoformans; or a diagnosis of CMV retinitis on ophthalmologic examination, should immediately disqualify a patient from treatment with NMAB. 
       Interval Monitoring In A Patient Undergoing Treatment With NMAB 
       [0012]    Because it is not clear whether PML is due to an infection with a latent JC Virus, or a JC Virus acquired by exposure after CNS immunosuppression due to NMAB or AIDS, and because likewise is the case for CMV, TB, EBV, Toxoplasma gondii, and Cryptococcus neoformans; it will be desirable to perform interval evaluations (and if necessary, interventions) of patients undergoing treatment with NMAB to reduce the risk of opportunistic disease resulting from CNS immunosuppression. 
         [0013]    Interval Monitoring for patients undergoing NMAB treatment can be divided into two categories: 
         [0014]    1) No Clinical Disease Progression: In this instance, a patient&#39;s history and physical exam demonstrate no progression of a patient&#39;s MS or other medical disorder, and no signs or symptoms of a potential opportunistic infection. As such, the Baseline Screening Evaluation should be performed on an annual basis and the patient&#39;s MS or other medical disorder should be treated according to standard treatment guidelines for the particular medical disorder. In this case, Interval Monitoring takes place on a regular annual basis. 
         [0015]    2) Clinical Disease Progression: In this instance, when a patient&#39;s history and/or physical exam indicate a progression of the underlying medical disorder such as MS, or symptoms and/or signs of a potential opportunistic disease process; an additional screening process (the Progression Screening Process) is undertaken immediately upon identifying the progression to rule out a CNS opportunistic disease process. This screening process incorporates the same group of studies indicated for the Baseline Screening Evaluation. Again, it is important to perform the MRI brain imaging studies prior to performing CSF studies as toxoplasmosis can create a mass effect that might make a lumbar puncture contraindicated. While the inventors are not aware of an identified case of toxoplasmosis in a patient undergoing NMAB treatment, toxoplasmosis is a well-known and treatable opportunistic infection of the CNS in immunocompromised patients. Should greater numbers of patients undertake NMAB therapy, this opportunistic infection may arise. Thus, this precaution of prioritizing brain MRI evaluation before CSF examination is reasonable.
       If MRI, CSF, or ophthalmologic examination of the Progression Screening Process uncovers an opportunistic CNS disease process, then NMAB therapy should be immediately discontinued and proper assessment and treatment of the identified opportunistic disease process should be undertaken.   If MRI, CSF, and ophthalmologic examination of the Progression Screening Process uncover no opportunistic disease, then a patient may continue NMAB therapy. In this case, within two weeks of the Progression Screening Process, a second lumbar puncture is performed to evaluate the CSF a second time (the Post-Progression Second Screen). Once again, the CSF is tested by PCR (or by another more sensitive assay if it is available) for one or more of CMV, JC Virus, EBV, TB, Toxoplasmosis, and Cryptococcus. The reason for the Post-Progression Second (CSF) Screen within two weeks of the Progression (CSF) Screen is the result of the imperfect sensitivity of PCR analysis. As examples, one diagnostic CSF PCR study for the JC Virus was 76% sensitive;       
 
         [0018]    another was 92% sensitive. Once a diagnostic study has a sensitivity of 99%, that particular CSF study can be eliminated from the Post-Progression Second (CSF) Screen.
       If both the Progression Screening Process and the Post-Progression Second Screen provide no indication of an opportunistic disease process within the CNS, then the ongoing treatment of the patient with MS (or other medical disorder) continues according to standard treatment guidelines for the particular medical disorder.   Subsequently, if a patient&#39;s history and physical exam then indicate no progression of the underlying medical disorder such as MS, nor symptoms nor signs of a potential opportunistic disease process, then a Baseline Screening Evaluation should be repeated one year after the last negative Post-Progression Second Screen.   However, if subsequently a patient&#39;s history and/or physical exam indicate a positive progression of the underlying medical disorder such as MS, and/or signs or symptoms of a potential opportunistic CNS disease process, then the time for the next Progression Screening Process should be at a minimum of two to three months following the last negative Post-Progression Second Screen.       
 
         [0022]    This Interval Monitoring continues for as long as a patient is treated with NMAB. 
         [0023]    To emphasize, the proposed method of screening and monitoring patients undergoing NMAB treatment for MS and other medical disorders, is intended to minimize, but will not eliminate, the risk of opportunistic CNS disease that may occur as a result of impaired CNS T-cell immunity due to NMAB therapy.