Targeting MDSC Differentiation Using ATRA: A Phase I/II Clinical Trial Combining Pembrolizumab and All-Trans Retinoic Acid for Metastatic Melanoma

PURPOSE

A phase Ib/II clinical trial was conducted to evaluate the safety and efficacy of the combination of all-trans retinoic acid (ATRA) with pembrolizumab in patients with stage IV melanoma.

PATIENTS AND METHODS

Anti-PD-1 naïve patients with stage IV melanoma were treated with pembrolizumab plus supplemental ATRA for three days surrounding each of the first four pembrolizumab infusions. The primary objective was to establish the MTD and recommended phase II dose (RP2D) of the combination. The secondary objectives were to describe the safety and toxicity of the combined treatment and to assess antitumor activity in terms of (i) the reduction in circulating myeloid-derived suppressor cell (MDSC) frequency and (ii) progression-free survival (PFS).

RESULTS

Twenty-four patients were enrolled, 46% diagnosed with M1a and 29% with M1c stage disease at enrollment. All patients had an ECOG status ≤1, and 75% had received no prior therapies. The combination was well tolerated, with the most common ATRA-related adverse events being headache, fatigue, and nausea. The RP2D was established at 150 mg/m2 ATRA + 200 mg Q3W pembrolizumab. Median PFS was 20.3 months, and the overall response rate was 71%, with 50% of patients experiencing a complete response, and the 1-year overall survival was 80%. The combination effectively lowered the frequency of circulating MDSCs.

CONCLUSIONS

With a favorable tolerability and high response rate, this combination is a promising frontline treatment strategy for advanced melanoma. Targeting MDSCs remains an attractive mechanism to enhance the efficacy of immunotherapies, and this combination merits further investigation. See related commentary by Olson and Luke, p. 1167.

Circulating CD8+ mucosal-associated invariant T cells correlate with improved treatment responses and overall survival in anti-PD-1-treated melanoma patients

Objectives

While much of the research concerning factors associated with responses to immune checkpoint inhibitors (ICIs) has focussed on the contributions of conventional peptide‐specific T cells, the role of unconventional T cells, such as mucosal‐associated invariant T (MAIT) cells, in human melanoma remains largely unknown. MAIT cells are an abundant population of innate‐like T cells expressing a semi‐invariant T‐cell receptor restricted to the MHC class I‐like molecule, MR1, presenting vitamin B metabolites derived from bacteria. We sought to characterise MAIT cells in melanoma patients and determined their association with treatment responses and clinical outcomes.

Methods

In this prospective clinical study, we analysed the frequency and functional profile of circulating and tumor‐infiltrating MAIT cells in human melanoma patients. Using flow cytometry, we compared these across metastatic sites and between ICI responders vs. non‐responders as well as healthy donors.

Results

We identified tumor‐infiltrating MAIT cells in melanomas across metastatic sites and found that the number of circulating MAIT cells is reduced in melanoma patients compared to healthy donors. However, circulating MAIT cell frequencies are restored by ICI treatment in responding patients, correlating with treatment responses, in which patients with high frequencies of MAIT cells exhibited significantly improved overall survival.

Conclusion

Our results suggest that MAIT cells may be a potential predictive marker of responses to immunotherapies and provide rationale for testing MAIT cell‐directed therapies in combination with current and next‐generation ICIs.

Melanoma Metastases to the Adrenal Gland Are Highly Resistant to Immune Checkpoint Inhibitors

BACKGROUND

Adrenal gland metastases (AGMs) are common in advanced-stage melanoma, occurring in up to 50% of patients. The introduction of immune checkpoint inhibitors (ICIs) has markedly altered the outcome of patients with melanoma. However, despite significant successes, anecdotal evidence has suggested that treatment responses in AGMs are significantly lower than in other metastatic sites. We sought to investigate whether having an AGM is associated with altered outcomes and whether ICI responses are dampened in the adrenal glands.

PATIENTS AND METHODS

We retrospectively compared ICI responses and overall survival (OS) in 68 patients with melanoma who were diagnosed with an AGM and a control group of 100 patients without AGMs at a single institution. Response was determined using RECIST 1.1. OS was calculated from time of ICI initiation, anti-PD-1 initiation, initial melanoma diagnosis, and stage IV disease diagnosis. Tumor-infiltrating immune cells were characterized in 9 resected AGMs using immunohistochemical analysis.

RESULTS

Response rates of AGMs were significantly lower compared with other metastatic sites in patients with AGMs (16% vs 22%) and compared with those without AGMs (55%). Patients with AGMs also had significantly lower median OS compared with those without AGMs (3.1 years vs not reached, respectively). We further observed that despite this, AGMs exhibited high levels of tumor-infiltrating immune cells.

CONCLUSIONS

In this cohort of patients with melanoma, those diagnosed with an AGM had lower ICI response rates and OS. These results suggest that tissue-specific microenvironments of AGMs present unique challenges that may require novel, adrenal gland-directed therapies or surgical resection.

Targeting the RIG-I-like receptor signaling pathway to improve the efficacy of immunotherapy in mucosal and uveal melanoma

e21593

Background: Patients with cutaneous (CM) or acral (AM) melanoma have high response rates to immune checkpoint blockade (ICB) therapies including anti-CTLA4, anti-PD1, and their combination. In contrast, patients with mucosal (MM) or uveal (UM) melanoma have low ICB response rates and a poorer overall prognosis. In this study, we analyzed melanoma transcriptomes to identify potential mechanisms underlying ICB resistance in MM and UM. We also evaluated epigenetic modifying drugs as potential agents to improve ICB responses in these patients. Methods: RNA sequencing was performed on 13 MM, 8 AM, and 24 CM patient-derived xenograft tumors. These data were analyzed along with published RNA sequencing data for 80 UM and 443 CM tumors. MM and UM cells were treated with several different classes of epigenetic modifying drugs, and the ICB-resistant YUMM1.7 mouse melanoma syngeneic model was used to evaluate the tumor growth effect of one particular drug, decitabine, at low (2.5 ug) and intermediate (10 ug) doses in combination with anti-PD1 (200 ug). Results: We identified 2513 differentially expressed genes (DEG) between MM and CM tumors (ANODEV adjusted p-value < 0.05, FDR < 0.1) compared to only 495 DEG between AM and CM. Ingenuity Pathway Analysis (IPA) analysis of the 2513 DEG in MM identified the RIG-I-like receptor (RLR) pathway as inhibited in MM versus CM ( p < 1x10-5). The RLR pathway was also inhibited in ICB-resistant CM versus ICI-sensitive (anti-CTLA4, p < 0.006 and anti-PD1, p < 0.0002) and in UM versus CM ( p < 1x10-8), but was not inhibited in AM. The RLR pathway is an innate immune pathogen sensing pathway that is critical for ICB responses in CM; therefore, we sought to identify FDA-approved drugs which activate the RLR pathway in MM and UM. Since RLR signaling is frequently repressed by epigenetic silencing, we screened direct DNMT1 inhibitors 5’-azacitidine (AZA) and 5’-aza-deoxycitidine (decitabine, DEC), several indirect DNMT1 inhibitors, and two HDAC inhibitors. We found that only DEC strongly induced the expression of RLR pathway genes in MM, UM, and ICB-resistant CM cells. Compared to vehicle, treatment of YUMM1.7 tumors with single agent anti-PD1 ( p > 0.87) and low dose ( p > 0.90) or intermediate dose ( p > 0.80) DEC had no effect on tumor growth. However, the addition of either low or intermediate dose DEC to anti-PD1 showed a trend of decreased tumor growth (low dose, 31% decrease, p = 0.22 and intermediate dose, 41% decrease, p = 0.55). Conclusions: We identified low RLR pathway signaling as one possible mechanism underlying ICB resistance in MM and UM. We show that an FDA-approved DNMT1 inhibitor, decitabine, strongly induces RLR pathway genes in MM and UM cells in vitro and leads to tumor growth suppression in combination with anti-PD1 in vivo. Therefore, co-administration of decitabine and anti-PD1 agents is a rational and novel strategy for improving outcomes for MM and UM patients.

Pembrolizumab and all-trans retinoic acid combination treatment of advanced melanoma

9536

Background: Myeloid-derived suppressor cells (MDSCs) are potent suppressors of antitumor immunity and are commonly associated with poor outcomes in melanoma patients treated with immune checkpoint inhibitors. Inducing the differentiation of MDSCs using all-trans retinoic acid (ATRA) reduces MDSC frequency. This analysis seeks to assess the safety and efficacy of combining ATRA and pembrolizumab in advanced melanoma patients. Methods: This single arm, single institution, phase I/II study (NCT03200847) enrolled 24 patients diagnosed with stage IV melanoma. Eligible patients were over the age of 18 and had not been previously treated anti-PD-1 therapy. Treatment consisted of 200mg Q3W pembrolizumab plus the supplemental treatment of 150 mg/m2 ATRA orally for 3 days surrounding each of the first four infusions of pembrolizumab, with patients continuing pembrolizumab for up to two years until confirmed disease progression or unacceptable toxicity. The primary endpoints were safety and reduction in circulating MDSCs. Secondary endpoints were overall response rate (ORR), disease control rate (DCR), progression free survival (PFS) according to RECIST v1.1. Results: At data cut off (Feb, 2021) 22 patients were evaluable for tumor response. Median follow-up was 1.0 years (0.3-2 years). In general, the combination of pembrolizumab and ATRA was well tolerated. The most common treatment-related adverse events (AEs) were grade 1 or 2, including headache (22 pts, 92%), fatigue (18 pts, 75%), rash (16 pts, 66%), and nausea (8 pts, 33%), most of which corresponded with the 3-day course of ATRA treatment. Ten patients had grade 3 or higher AEs with most being common ICI-related AEs. The ORR was 60% and DCR was 83%. Six-month PFS rate was 62%. Excluding patients diagnosed with uveal melanoma (n = 2) the ORR was 72%, DCR was 86%, and the six-month PFS rate was 68%. Paired analysis showed sustained decreases in absolute numbers ( p = 0.002) and percentage ( p = 0.007) of circulating MDSCs (CD3-CD19-CD56-CD11b+CD33+HLA-DR-/low) 4-6 weeks after stopping ATRA. The study is ongoing and further data will be presented in the future. Conclusions: This study demonstrates that the combination of ATRA and pembrolizumab is well tolerated and suggests that reducing MDSCs with ATRA may enhance the efficacy of pembrolizumab. This strategy of targeting MDSCs in combination with pembrolizumab warrants further development. Research Funding: Merck. Clinical trial information: NCT03200847.

Developing preliminary blood metabolomics-based biomarkers of insufficient sleep in humans

STUDY OBJECTIVE

Identify small molecule biomarkers of insufficient sleep using untargeted plasma metabolomics in humans undergoing experimental insufficient sleep.

METHODS

We conducted a crossover laboratory study where 16 normal-weight participants (eight men; age 22 ± 5 years; body mass index < 25 kg/m2) completed three baseline days (9 hours sleep opportunity per night) followed by 5-day insufficient (5 hours sleep opportunity per night) and adequate (9 hours sleep opportunity per night) sleep conditions. Energy balanced diets were provided during baseline, with ad libitum energy intake provided during the insufficient and adequate sleep conditions. Untargeted plasma metabolomics analyses were performed using blood samples collected every 4 hours across the final 24 hours of each condition. Biomarker models were developed using logistic regression and linear support vector machine (SVM) algorithms.

RESULTS

The top-performing biomarker model was developed by linear SVM modeling, consisted of 65 compounds, and discriminated insufficient versus adequate sleep with 74% overall accuracy and a Matthew's Correlation Coefficient of 0.39. The compounds in the top-performing biomarker model were associated with ATP Binding Cassette Transporters in Lipid Homeostasis, Phospholipid Metabolic Process, Plasma Lipoprotein Remodeling, and sphingolipid metabolism.

CONCLUSION

We identified potential metabolomics-based biomarkers of insufficient sleep in humans. Although our current biomarkers require further development and validation using independent cohorts, they have potential to advance our understanding of the negative consequences of insufficient sleep, improve diagnosis of poor sleep health, and could eventually help identify targets for countermeasures designed to mitigate the negative health consequences of insufficient sleep.

0050 Identification of a Plasma Metabolome-Based Biomarker for Dim-Light Melatonin Offset and Onset in Humans

Introduction

Easily measuring individual circadian timing is increasingly important to inform personalized chronotherapy, screen for circadian disorders and circadian misalignment, and advance circadian research. Findings from multiple studies show that transcriptomics is a viable method to estimate dim-light melatonin onset (DLMO), but no published omics-based findings have predicted dim-light melatonin offset (DLMOff), and only one known study has used metabolomics to predict DLMO. Here, we developed and tested a plasma metabolomics-based biomarker of circadian phase using DLMO and DLMOff as phase markers.

Methods

Sixteen (8M/8F) healthy participants aged 22.4 ± 4.8y (mean ± SD) completed an in-laboratory study with 3 baseline days (9h sleep opportunity/night), followed by a randomized cross-over protocol with 9h sleep and 5h sleep conditions, each lasting 5 days. Blood was collected every 4h on the final 24h of each condition for untargeted metabolomics analyses. DLMO and DLMOff were determined during the final 24h of each condition. Samples from all conditions were randomly split into training (68%) and test (32%) datasets. DLMO and DLMOff models were developed using partial least squares regression in the training dataset and validated in the test dataset.

Results

When validating with the test dataset, R2 for the DLMO model was 0.60, median absolute error (MdAE) was 2.2 ± 2.8h (± interquartile range), and 44% of samples had MdAE under 2h. R2 for the DLMOff model was 0.62, MdAE was 1.8 ± 2.6, and 51% of samples had MdAE under 2h. The DLMOff model predicted baseline samples, under conditions of 9h sleep and controlled food intake, with an R2 of 0.91 and MdAE 1.1 ± 1.1h.

Conclusion

These findings show promise for metabolomics-based biomarkers of circadian phase and highlight the need for biomarker efforts to predict multiple circadian phase markers. Additional analyses with an independent validation dataset will help advance these initial findings.

Support

NIH-R01HL085705, NIH-R01HL109706, NIH-R01HL132150, NIH-K01HL145099, NIH-F32DK111161, and NIH-UL1TR000154; and Sleep Research Society Foundation 011-JP-16;