L-Tetrahydropalmatine, a Novel Dopamine Antagonist, Fails to Improve Psychiatric Symptoms as Adjunctive Treatment for Schizophrenia.

Seventy-four subjects enrolled, of whom 63 were randomized and 58 completed the study (26 in the l-THP group and 32 in the placebo group; figure 1 ). The baseline demographic and clinical characteristics did not differ significantly between the two medication groups, except that the l-THP group had a higher proportion of participants taking anticholinergic medication (21% vs 3%, respectively; table 1 ). Baseline demographic and clinical characteristics of subjects Note : Data presented as mean ± SD, unless otherwise specified. FGA, first-generation antipsychotic; SGA, second-generation antipsychotic. Participant randomization and flowchart. L-THP had no significant effect on any psychiatric symptom measure or cognitive function ( table 2 ). One person in the l-THP group had >50% improvement in total BPRS score. Psychiatric symptoms before and after four weeks of levo-tetrahydropalmatine (l-THP) administration Note : Statistics reported as time by treatment interaction. Data reported as mean ± SD. BPRS, Brief Psychiatric Rating Scale; CDS, Calgary Depression Rating Scale; CGI, Clinical Global Impression Scale; Endpoint, end of treatment; ES, Cohen’s effect size; MCCB, MATRICS Consensus Cognitive Battery; SANS, Scale for the Assessment of Negative Symptoms. The medication was well tolerated, with no significant medication group differences in incidence or intensity of side effects ( table 3 ). L-THP was associated with a significant decrease in extrapyramidal symptoms, compared with placebo, as assessed by the SAS ( table 3 ). There was no difference in weight change or suicidality between the two groups, nor any between-group differences in vital signs (pulse, temperature, and blood pressure), blood chemistry, and lipid panels. There was no change in serum prolactin levels after 4 weeks of treatment ( F = 1.01, df = 1,56, P = .32). Side effects during 4 weeks of levo-tetrahydropalmatine (l-THP) administration Note : Values presented as mean ± SD. Statistical analysis by Fisher’s exact test for Side Effect Checklist by ANCOVA for the rest of the measures. BAS, Barnes Akathisia Scale; BMI, body mass index; df, degrees of freedom; ES, Cohen’s effect size; SAS, Simpson Angus Extrapyramidal Symptom Rating Scale. The two medication groups did not differ significantly at baseline in peripheral concentrations of plasma inflammatory markers ( table 4 ). Four weeks of l-THP exposure was associated with significantly increased plasma concentration of 2 of the 11 inflammatory markers measured: sICAM-1 and CRP ( table 4 ). Plasma concentrations of peripheral inflammatory markers during 4 weeks of levo-tetrahydropalmatine (l-THP) treatment Note : Values reported as mean change ± SD; Wilcoxon test. Mean change represents change between weeks 0 and 4; F -statistic represents treatment by time interaction. CRP, C-reactive protein; df, degrees of freedom; IFN, interferon; IL, interleukin; sICAM, soluble intracellular adhesion molecule; TNF, tumor necrosis factor.

Participants were recruited from both inpatient and outpatient status at the Maryland Psychiatric Research Center and affiliated clinical sites in the Baltimore, MD, metropolitan region. Potentially eligible participants were identified by review of medical records, with the diagnosis of schizophrenia confirmed by a structured psychiatric diagnostic interview (Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders , Fourth Edition [SCID-IV]). Inclusion criteria for study participation were as follows: (1) Diagnostic and Statistical Manual of Mental Disorders , Fourth Edition (DSM-IV) diagnosis of schizophrenia or schizoaffective disorder, (2) minimum score of 45 on the Brief Psychiatric Rating Scale, or a Clinical Global Impression (CGI) score of 4, (3) age 18–64 years, (4) currently taking an antipsychotic regimen with no dose changes in the last 30 days, and (5) ability to provide valid informed consent as determined by a score of 10 or greater on the Evaluation to Sign Consent. 32 Exclusion criteria included (1) women who were pregnant or capable of getting pregnant, (2) current diagnosis of organic brain disorder or mental retardation, (3) medical condition that could alter the presentation or treatment of schizophrenia or significantly increase the risk associated with study medication, (4) substance abuse or dependence in the last month as diagnosed by DSM-IV criteria (other than nicotine or caffeine), (5) inability to understand English, (6) inability to cooperate with study procedures, and (7) taking herbal or homeopathic medications with unknown metabolic pathways. Participants who may have met criteria for treatment resistance were not excluded from this study. This study was approved by the University of Maryland Institutional Review Board (IRB) and the State of Maryland Department of Health IRB, which relied on the University of Maryland, Baltimore IRB. All participants gave written informed consent prior to starting the study. L-THP was dosed as one capsule (30 mg) twice daily (matching placebo or L-THP; total 60 mg daily). Medication dose, study duration, and adjunct treatment were guided by an Investigational New Drug (IND) approval from the Food and Drug Administration (IND 121776). L-THP and matching placebo capsules were prepared at the University of Maryland School of Pharmacy Applied Pharmaceutics Laboratory (APhL). Identical placebo and active capsules were made in accordance with Good Manufacturing Practices standards for clinical trials. The capsules were filled using Active Pharmaceutical Ingredient (API) obtained from the WuxiGorunjie Technology Co., Ltd., Jiangsu, China. The identity, purity, and quality of the API and the final capsules were evaluated in the APhL using standard methods. Participants were randomized into placebo and L-THP groups using separate permuted block randomization sequences. Only the study pharmacist knew the group assignments. Participants were given a supply of their study medication on a weekly basis. Study medication was used as an adjunct treatment only, and all study participants were on a stable dose of a primary antipsychotic medication throughout the 4-week duration of the study. At baseline, participants underwent a medical work-up that included a comprehensive medical history and physical examination, baseline, midpoint, and end-of-study Electrocardiogram, Complete Blood Count, chemistry panel, liver enzymes, thyroid panel, and urinalysis. Safety and tolerability measurements and vital signs were assessed weekly throughout the trial. Study participants were regularly assessed at each study visit for adherence, and research staff reminded participants weekly to be taking medication. Forty-six percent of participants missed no doses, 45% missed 1–2 doses, and 9% missed more than 2 doses. Sample size was too small in the groups with missing doses to examine results separately. The primary symptom outcomes for this study were positive and negative symptoms of schizophrenia. Psychological symptoms were assessed using the Brief Psychiatric Rating Scale (BPRS) positive symptoms item score, 33 Schedule for Assessment of Negative Symptoms (SANS) total score, 34 Calgary Depression Rating Scale (CDS) total score, 35 and CGI Scale. 36 Neurocognition was measured using the MATRICS Consensus Cognitive Battery (MCCB). 37 , 38 The following assessments were performed weekly throughout the study: Simpson Angus Extrapyramidal Symptom Rating Scale (SAS), 39 Barnes Akathisia Scale (BAS), 40 Side Effect Checklist (SEC) ( table 3 ), and the Columbia Suicide Severity Rating Scale (C-SSRS). 41 Peripheral venous blood was collected, centrifuged, and stored at −80°C until completion of the study. Plasma TNF-α, IL-6, soluble intracellular adhesion molecule 1 (sICAM-1), and IL-1 β, IL-2, IL-8, IL-10, IL-12, IL-17A, INFɣ, and highly sensitive C-reactive protein (hs-CRP) were measured in sera collected at study baseline (week 0) and at the end of the study (week 4) with quantitative ELISA kits from R&D Systems (Fisher Scientific) using a monoclonal antibody specific for the cytokine being tested. Standards, controls, and study samples were all tested at the same time. The sample values were read from a standard curve. All measurements were done on a SpectraMax 384 (Molecular Devices) absorbance microplate reader. Our primary symptom outcome was the BPRS psychosis score and SANS total score, assessed at baseline, midpoint, and end of study. We analyzed these two primary outcomes (as well as secondary outcomes, Calgary Depression Rating Scale, collected on the same schedule) with the intent to treat analyses using mixed models for unbalanced repeated measures (MMRM) ANCOVA, including all available observations from participants who completed at least one follow-up rating. Use of mixed models has the advantages that data from participants who drop out early can be included in the analysis and that estimates of treatment effects will be unbiased by dropout if reasons for dropout are ignorable with respect to the outcome, given the observed data. These models had the basic form: follow-up score = baseline score + week + treatment + treatment × week, where week is a set of categorical indicators defining which week the follow-up score came from. The primary test for treatment effect was a post hoc contrast from the MMRM outlined above, comparing the mean outcomes scores at week 4, adjusted for baseline, in study participants assigned to l-THP or placebo. We had chosen to focus on week 4 differences because of uncertainty about when treatment differences would emerge in the two strata. Secondary outcome measures collected at baseline and end of study were analyzed as follows: change scores for cytokines, which have highly skewed distributions, were analyzed using the Wilcoxon rank sum test. The MCCB composite score, a normed average of the T -scores representing different cognitive domains, was our primary neurocognitive outcome measure and was analyzed using ANCOVA, adjusting for baseline MCCB composite score. With n = 60 study participants, we estimated approximate power for the primary outcome using the main effect of treatment in a simple ANCOVA, adjusting for baseline. The effect size E , detectable by a repeated measures ANCOVA for a given sample size, n , per group is given by: E 2 = 2( z 1 − α/2 + z 1 − β ) 2 (1 − ρ  0 2 )/ n , where z 1-α/2 and z 1-β are the quantiles of the normal distribution corresponding to the specified type I error rate and power, respectively. In this formula, the term (1 − ρ  0 2 ) reflects the reduction in the variance in follow-up scores from adjusting for the baseline score. A sample size of 60 had power to detect an effect size of d = 0.57 if ρ  0 = 0.7 or d = 0.48 for ρ  0 = 0.8. For the MCCB composite score, we had power = 0.8 to detect an effect size d = 0.349 on the MCCB composite with the a priori defined sample size of 60.

As far as we are aware, this is the first randomized, double-blind, placebo-controlled study of l-THP as an adjunctive treatment for schizophrenia. Given the D1, D2, and D3 dopamine receptor antagonism properties of l-THP, we hypothesized that l-THP, when added to a stable dose of an antipsychotic medication, would lead to an improvement of positive and negative symptoms of schizophrenia. However, 4 weeks of l-THP treatment was not associated with any significant change in psychiatric measures. L-THP was well tolerated by people with schizophrenia and significantly decreased extrapyramidal side effects (EPS) as measured by the Simpson Angus Extrapyramidal Symptom Scale. However, the EPS effect may have been confounded by a greater number of l-THP treatment participants taking anticholinergic medication. Interaction between l-THP and anticholinergic medications has not been previously reported but cannot be excluded. Our use of l-THP as an add-on treatment, done for ethical reasons, may have limited our ability to detect an antipsychotic effect. The mean baseline CGI for study participants represents a moderately ill population. Study participants were already on a stable dose of an antipsychotic medication, so any additional dopamine blockade or other antipsychotic action provided by l-THP may have not been enough to generate a clinically observable change in symptoms. Our study did not evaluate l-THP as a primary antipsychotic, which remains to be tested. The 4-week duration of treatment is unlikely to have limited any antipsychotic effects as conventional antipsychotic medications start to show antipsychotic effects within 1 month. 42 L-THP is reported to have several active metabolites, including l-isocorypalmine and l-corydalmine, which have been previously isolated in rodent models. 43–46 We did not examine metabolism of l-THP and the presence of active metabolites in the current study. This is the first study of which we are aware to evaluate the effect of l-THP on inflammatory markers in human participants. Given the previously reported anti-inflammatory effects of l-THP in preclinical models, 22–25 we expected a decrease in peripheral inflammatory markers. Contrary to our hypothesis, we did not observe any significant decrease in plasma concentrations of the 11 inflammatory markers we measured. To the contrary, plasma concentrations of two markers, sICAM-1 and CRP, were elevated in the l-THP group. ICAM-1 exists as a membrane-bound molecule found in leukocytes, microglia, and astrocytes in the Central Nervous System (CNS) and as a soluble form (sICAM-1) found in body fluids, including peripheral blood and the CNS. sICAM-1 can be detected in the serum and in vitro studies suggest a direct correlation between sICAM-1 and membrane-bound ICAM-1 found in the brain, where it plays a role in the maintenance of the blood-brain barrier and is a marker for inflammation. 47 In unmedicated people with schizophrenia, peripheral blood sICAM-1 levels are lower than in healthy controls;  8 however, several recent studies suggest that sICAM-1 levels are increased in people treated with an antipsychotic medication. 48 , 49 L-THP increased sICAM-1 levels in the current study, suggesting that it acts through a mechanism similar to that of other antipsychotic medications. Notably, in unmedicated and medicated people with schizophrenia, sICAM-1 levels are correlated positively with severity of negative symptoms and duration of disease. 50 We did not observe a change in positive or negative symptoms of schizophrenia, despite an elevation in sICAM-1 in this 4-week study. This result suggests that variable sICAM-1 levels may reflect different subgroups of people with schizophrenia. In summary, we found that adjunctive treatment with l-THP had no effect on psychiatric symptoms in people with schizophrenia, although we did observe a decrease in extrapyramidal symptoms. We also found an elevation in sICAM-1 and CRP after treatment with l-THP in the first study to evaluate the effect of l-THP on inflammatory markers in human participants.

Schizophrenia is a complex mental health illness with multiple behavioral manifestations. To date, all approved pharmacological treatments for schizophrenia have focused on modulation of the dopamine system. There is a growing literature suggesting involvement of inflammatory processes in the pathogenesis of schizophrenia. 1 One marker of inflammation, tumor necrosis factor-α (TNF-α), is consistently elevated in people with schizophrenia, 1 and promising anti-inflammatory treatment approaches have been described. 2 , 3 In this study, we evaluated a novel plant-derived medication, levo-tetrahydropalmatine (l-THP), with previously reported anti-inflammatory and antipsychotic-like properties 4 , 5 as a potential adjunctive treatment for people with schizophrenia. L-THP is marketed in China (trade name Rotundine) for sedative and analgesic purposes. Short-term (up to 4 weeks) controlled clinical trials found l-THP safe and well tolerated in patients with substance use disorders. 6–8 Animal data suggest that l-THP may have utility in treating endometriosis pain because of its anti-inflammatory properties 9 , 10 and may have a neuroprotective effect following ischemia-reperfusion injury. 11 L-THP acts as a dopamine receptor antagonist, with modest intrinsic activity and higher affinity for D1 than D2 receptors, making it more similar to clozapine than to first-generation antipsychotics. 12 Consistent with its action at dopamine receptors, l-THP has recently been implicated in reward behaviors in humans and rodents. 6 , 13–16 Dopaminergic action also appears to mediate the compound’s analgesic and hypnotic effects in mice. 17 L-THP also functions as a positive allosteric modulator of gamma amino butyric acid (GABA) A receptors, modulator of alpha-2 adrenergic and 5-HT 1A receptors, and as an MAO-I inhibitor. 18–20 It inhibits neuronal excitability in primary neuronal cultures, 21 suggestive of a neuroprotective effect. L-THP appears to have anti-inflammatory effects in preclinical models. L-THP decreases activity of the proinflammatory cytokines tumor necrosis factor-α (TNF-α) and interleukin 6 (IL-6), possibly via suppression of NF-κB expression. 22–25 Consistent with this, l-THP downregulates the ERK/NF-κB pathway following hepatocyte injury. 26 ICAM-1 is a member of the immunoglobulin superfamily of genes and functions as an adhesion molecule. ICAM-1 is constitutively expressed in endothelial cells and its expression is enhanced by inflammatory cytokines, such as IL-6 and TNF-α. 27 Soluble (s)ICAM-1 is found in sera and is increased during inflammation and cell damage. In human umbilical vein endothelial cells, l-THP dose-dependently decreases levels of I-CAM, vascular cell adhesion molecule-1, and E-selectin, which is consistent with studies that have reported a decrease in TNF-α. 28 , 29 L-THP also decreases levels of metalloproteinase, a mediator of inflammation, which is consistent with an anti-inflammatory role. 30 , 31 We are not aware of any studies of l-THP in people with schizophrenia, nor of any human studies evaluating anti-inflammatory effects of l-THP. In this controlled clinical trial, we tested the use of L-THP as an adjunctive treatment in adults with schizophrenia on a stable dose of antipsychotic medication. We assessed both treatment efficacy and effect on levels of peripheral inflammatory markers, with the hypothesis that adjunctive l-THP would improve positive and negative symptoms of schizophrenia and be well tolerated.