L-methylfolate augmentation of selective serotonin reuptake inhibitors (SSRIS) for major depressive disorder: Results of two randomized, double-blind trials

Introduction

Two randomized, controlled trials of L-methylfolate augmentation of SSRIs for major depressive disorder (MDD) were conducted using a novel study design (sequential parallel comparison design- SPCD).

Objectives/aims

To evaluate the efficacy of L-methylfolate augmentation using the Hamilton Depression Rating Scale.

Methods

In study one (TRD-1), 148 outpatients with SSRI-resistant MDD were enrolled in a 60-day, SPCD study, divided into two 30-day periods (phases 1 and 2). Patients were randomized 2:3:3 to receive L-methylfolate (7.5mg/d in phase 1, 15mg/d in phase 2), placebo in phase 1 followed by L-methylfolate 7.5mg/d in phase 2, or placebo for both phases. Study two (TRD-2) involved 75 patients and was identical in design to TRD-1 except for the dose of L-methylfolate (15mg only).

Results

In the TRD-1 Study, L-methylfolate 7.5 mg/d was not found to be more effective than placebo. In phase 1 of the TRD-2 Study, 37% of patients on L-methylfolate 15mg/d responded and 18% of placebo patients responded, while in phase 2 among placebo non-responders, the response rates were 28% on L-methylfolate 15mg/d and 9.5% on placebo. When phases 1 and 2 were pooled according to the SPCD model, the difference in response rates was statistically significant in favor of L-methylfolate (p = 0.0399). The rates of spontaneously reported AEs and rates of study discontinuation appear r comparable between L-methylfolate and placebo in both studies. Rates of study discontinuation were also comparable

Conclusions

These studies suggest that L-methylfolate 15 mg/d may be a safe and effective augmentation strategy for inadequate response to SSRIs.

Characterization of immune responses to anti-PD-1 mono and combination immunotherapy in hematopoietic humanized mice implanted with tumor xenografts

Background

The success of agents that reverse T-cell inhibitory signals, such as anti-PD-1/PD-L1 therapies, has reinvigorated cancer immunotherapy research. However, since only a minority of patients respond to single-agent therapies, methods to test the potential anti-tumor activity of rational combination therapies are still needed. Conventional murine xenograft models have been hampered by their immune-compromised status; thus, we developed a hematopoietic humanized mouse model, hu-CB-BRGS, and used it to study anti-tumor human immune responses to triple-negative breast cancer (TNBC) cell line and patient-derived colorectal cancer (CRC) xenografts (PDX).

Methods

BALB/c-Rag2^nullIl2rγ^nullSIRPα^NOD (BRGS) pups were humanized through transplantation of cord blood (CB)-derived CD34+ cells. Mice were evaluated for human chimerism in the blood and assigned into experimental untreated or nivolumab groups based on chimerism. TNBC cell lines or tumor tissue from established CRC PDX models were implanted into both flanks of humanized mice and treatments ensued once tumors reached a volume of ~150mm³. Tumors were measured twice weekly. At end of study, immune organs and tumors were collected for immunological assessment.

Results

Humanized PDX models were successfully established with a high frequency of tumor engraftment. Humanized mice treated with anti-PD-1 exhibited increased anti-tumor human T-cell responses coupled with decreased Treg and myeloid populations that correlated with tumor growth inhibition. Combination therapies with anti-PD-1 treatment in TNBC-bearing mice reduced tumor growth in multi-drug cohorts. Finally, as observed in human colorectal patients, anti-PD-1 therapy had a strong response to a microsatellite-high CRC PDX that correlated with a higher number of human CD8+ IFNγ+ T cells in the tumor.

Conclusion

Hu-CB-BRGS mice represent an in vivo model to study immune checkpoint blockade to human tumors. The human immune system in the mice is inherently suppressed, similar to a tumor microenvironment, and thus allows growth of human tumors. However, the suppression can be released by anti-PD-1 therapies and inhibit tumor growth of some tumors. The model offers ample access to lymph and tumor cells for in-depth immunological analysis. The tumor growth inhibition correlates with increased CD8 IFNγ+ tumor infiltrating T cells. These hu-CB-BRGS mice provide a relevant preclinical animal model to facilitate prioritization of hypothesis-driven combination immunotherapies.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0518-z) contains supplementary material, which is available to authorized users.