How can we best care for people with dementia with Lewy bodies pharmacologically?

KEYWORDS:

• dementia with Lewy bodies
• key symptoms
• pharmacotherapy
• side effects
• atypical antipsychotic
• immunotherapy

1. Introduction

Dementia with Lewy bodies (DLB), the second most common neurodegenerative dementia after Alzheimer’s disease (AD), and Parkinson’s disease-dementia (PDD), according to DSM-5 [1], are major neurocognitive disorders with Lewy bodies (LB) (1). The two entities that are likely to represent different points along a LB disease spectrum with genetic, clinical and pathological overlap [2], are demarcated from each other by the arbitrary ‘1-year rule’: diagnosis of DLB is more likely if cognitive impairment develops within one year before the onset of parkinsonian motor signs, while PDD is more likely if dementia develops after at least one year [3]. However, DLB patients may initially present with cognitive decline without any motor disability and about 25% of them never develop parkinsonian symptoms [2]. DLB is a heterogeneous disorder with a wide range of cognitive, psychiatric, sleep, motor and autonomic symptoms. Besides cognitive impairment (dementia), often preceding parkinsonism, DLB patients must have two of four clinical core features: visual hallucinations, parkinsonism, cognitive fluctuations, or REM sleep behavior disorder (RBD) [3]. Although clinical guidelines outline some treatment options for patients with DLB and PDD (National Institute for Health and Care Excellence/NICE 2019), no comprehensive guide to the pharmacological management of these patients exists [4], and there are no officially approved drugs for its treatment in the USA and EU. The evidence-based treatments of key domains of cognitive impairment, motor, autonomic and other symptoms have been reviewed recently [3–8], as well as non-pharmacological approaches, but larger trials evaluating non-pharmacological interventions for DLB are needed [4,9,10]. In general, the currently available therapies for DLB (and PDD) fail to modify the disease progression and neurodegeneration, and LBD treatments being mostly symptomatic show only a temporary and modest clinical effect [8].

Robust evidence exists for the efficacy of cholinesterase inhibitors (ChEIs) in the treatment of cognitive and neuropsychiatric symptoms in DLB (and in PDD), based on the marked loss of acetylcholine neurons in DLB [8]. Meta-analyses indicated beneficial effects of both donepezil and rivastigmine [11], the first drug being approved for use for DLB in Japan and the Philippines [6]. A systematic review suggested that donepezil but not rivastigmine, might reduce hallucinations and cognitive fluctuations in DLB patients [12], while these drugs did not improve visuospatial cognition. Memantine, an NMDA receptor agonist, had significant effects on attention and executive function, without significant adverse effects [11]. Rivastigmine, but not donepezil and memantine, was associated with greater risk of adverse effects in DLB [12]. If despite ChEIs and memantine treatment, psychotic symptoms remain, antipsychotic drugs may be considered despite the high risk of severe, potentially life-threatening sensitivity reactions that might occur in DLB patients. This needs high caution in their use in order to reduce the risk of neuroleptic morbidity [3]. Atypical antipsychotic agents, such as quetiapine or clozapine should be used in cases of agitation and other severe neuropsychiatric symptoms, but the dose may be limited to avoid parkinsonian or epileptogenic side effects [6]. Recent studies have shown that low doses of valproic acid (or divalproex) can be used as adjunct drugs. Primavanserin (NCT03325556), a new antiepileptic drug with antagonism for the 5-HT2a receptor, approved by the FDA for the treatment of psychosis in PD, may also be used for DLB patients [4]. Depression occurs in about one-third of DLB patients, but there is currently no evidence supporting the use of antidepressants in this disease, even though patients are commonly treated with second-generation antidepressants (selective serotonin reuptake inhibitors/SSRIs, serotonin-norepinephrine reuptake inhibitors/SNRIs, tradozone or mirtazapine, a noradrenergic-specific serotonergic antidepressant). However, trials with these drugs have not yet been performed. Moreover, there are concerns that antidepressants may worsen RBD symptoms. Melatonin, a hormone produced by the pineal gland which regulates sleep and wakefulness, has been demonstrated to reduce the frequency and severity of RBD, but larger trials will be needed [6,7]. The same holds true for nelotanserin, a 5-HT2A inverse agonist that was initially developed for the treatment of chronic insomnia [6]. Excessive daytime sleepiness is common in DLB patients, but its management is challenging, and the efficacy of various treatments, such as caffeine, atomoxetine or sodium oxybate, has been insufficient [4].

The parkinsonism of DLB is difficult to treat although levodopa was generally well tolerated, but produced less motor response in DLB than in PDD [12]. Furthermore, it may be associated with an increased risk of psychiatric side effects [4]. A recent trial reported significant improvement of motor functions in DLB patients when zonisamide, an antiepileptic drug, was used as an adjuvant treatment to low doses of levodopa [13]. DLB patients should be followed thoroughly, carefully balancing potential benefits versus potential side effects, for example the use of both levodopa and antipsychotic drugs. Despite the prominence and severity of autonomic signs and symptoms in DLB patients, no evidence base is yet established for their successful treatment, and no trials with specific drugs have been specifically conducted for autonomic disorders in LBD, such as gastrointestinal dysfunction, orthostatic hypotension, or urinary symptoms, which are usually treated symptomatically with a wide range of medications also used for PD [4].

Several novel drugs are currently being tested in clinical trials as potential disease-modifying agents for DLB that should focus on reducing toxic levels of α-synuclein (αSyn), such as ambroxol, a drug currently available for treatment of respiratory diseases that has anti-inflammatory properties and improves lysosomal biochemistry, thus having the potential to slow progression of neurodegeneration, or E2027, a phosphodiesterase-1-inhibitor, that may reduce αSyn toxicity [6]. Strategies to decrease the level of αSyn by inhibiting aggregation or promoting its degradation to prevent cell-to-cell transmission of misfolded αSyn [14], and deep brain stimulation of the cholinergic nucleus basalis of Meynert and transcranial direct current stimulation have been discussed [2,4]. The contribution of neuroinflammation to the progression of the disease and the prion-like hypothesis which enables targeting the extracellular transmission of αSyn, make immunotherapy probable as the most promising therapeutic approach for DLB and PDD [14,15]. Preliminary results of anti-αSyn vaccination in a combined model of synucleinopathy, which could be combined with anti-neuroinflammation agents may open the way to potential new treatments [6,15].

2. Expert opinion

To date, there is no drug with disease-modifying effects for DLB available, and the treatment is mostly symptomatic, trying to counterbalance the underlaying neurotransmission disturbances. Given its complex phenotype, the management of DLB is challenging, especially in view of the limited evidence about specific interventions [4,8]. The lack of effective therapies for DLB is, at least partially, due to our shortage of detailed understanding of the molecular mechanisms of this devastating disorder. We need to improve our knowledge of the underlaying molecular mechanisms and identify new targets for therapeutic intervention. The benefits of ChEIs and memantine in DLB for treating cognitive and behavioral deficits are well established, and agitation and psychosis can be managed with low doses of atypical antipsychotic drugs like quetiapine and clonazepam, while psychiatric side effects associated with levodopa can be managed by using zonisamide or valproic acid as adjuncts to low doses of levodopa, although the latter two’s possible effect on DLB is still based on limited studies. A number of clinical trials assessing treatment interventions in patients with DLB are currently under way, such as serotonin receptor agonists and antagonists, enhancers of dopamine receptor D1, agonists of melatonin receptors, tyrosine kinase inhibitor, as well as potential disease-modifying therapy agents, etc., which are awaiting results in the near future [4]. Furthermore, strategic drug combinations or multiple-target drugs can be utilized, and immunotherapies against αSyn, probably combined with anti-neuroinflammation agents [16], could show synergistic outcomes by inhibiting several pathogenic molecular pathways at different levels. Treatment of any single symptom should not be performed in isolation, and a multispecialist or interdisciplinary approach combining multi-target drugs and various approaches may provide some potential benefits. International strategic efforts, such as the Lewy Body Dementia Association’s Research Centers of Excellence Program [17], that was established to increase patient access to clinical experts, are also providing important research infrastructure to support such work, and resources are needed to develop collaborative efforts to manage LBD and its substantial symptoms. The costs for and needs of LBD patients are high and the management is complex, but the potential benefits of properly managing LBD, possibly its molecular backgrounds and its wide array of symptoms may be substantial.

Declaration of interest

The author has no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer Disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This manuscript was not funded.