Aerosol azacytidine inhibits orthotopic lung cancers in mice through Its DNA demethylation and gene reactivation effects

Targeting EZH2 to overcome the resistance to immunotherapy in lung cancer

Unleashing the immune system to fight cancer has been a major breakthrough in cancer therapeutics since 2014 when anti-PD-1 antibodies (pembrolizumab and nivolumab) were approved for patients with metastatic melanoma. Therapeutic indications have rapidly expanded for many types of advanced cancer, including lung cancer. A variety of antibodies targeting the PD-1/PD-L1 checkpoint are contributing to this paradigm shift. The field now confronts two salient challenges: first, to improve the therapeutic outcome given the low response rate across the histologies; second, to identify biomarkers for improved patient selection. Pre-clinical and clinical studies are underway to evaluate combinatorial treatments to improve the therapeutic outcome paired with correlative studies to identify the factors associated with response and resistance. One of the emerging strategies is to combine epigenetic modifiers with immune checkpoint blockade (ICB) based on the evidence that targeting epigenetic elements can enhance anti-tumor immunity by reshaping the tumor microenvironment (TME). We will briefly review pleotropic biological functions of enhancer of zeste homolog 2 (EZH2), the enzymatic subunit of polycomb repressive complex 2 (PRC2), clinical developments of oral EZH2 inhibitors, and potentially promising approaches to combine EZH2 inhibitors and PD-1 blockade for patients with advanced solid tumors, focusing on lung cancer.

First-in-human study of inhaled Azacitidine in patients with advanced non-small cell lung cancer

BACKGROUND

Aerosolized Azacitidine has been shown to inhibit orthotopic lung cancer growth and induce re-expression of methylated tumor suppressor genes in murine models. We hypothesized that inhaled Azacitidine is safe and effective in reversing epigenetic changes in the bronchial epithelium secondary to chronic smoking.

PATIENTS AND METHODS

We report the first in human study of inhaled Azacitidine. Azacitidine in aqueous solution was used to generate an aerosol suspension of 0.25-5 μm particle size. Main inclusion criteria: Stage IV or recurrent NSCLC with predominantly lung involvement, ≥1 prior systemic therapy, ECOG PS 0-1, and adequate pulmonary function. Patients received inhaled Azacitidine daily on days 1-5 and 15-19 of 28-day cycles, at 3 escalating doses (15, 30 and 45 mg/m² daily). The primary objective was to determine the feasibility and tolerability of this new therapeutic modality. The key secondary objectives included pharmacokinetics, methylation profiles and efficacy.

RESULTS

From 3/2015 to 2/2018, eight patients received a median number of 2 (IQR = 1) cycles of inhaled Azacitidine. No clinically significant adverse events were observed, except one patient treated at the highest dose developed an asymptomatic grade 2 decreased DLCO which resolved spontaneously. One patient receiving 12 cycles of therapy had an objective and durable partial response, and two patients had stable disease. Plasma Azacitidine was only briefly detectable in patients treated at the higher doses. Moreover, in 2 of 3 participants who agreed and underwent pre- and post-treatment bronchoscopy, the global DNA methylation in the bronchial epithelium decreased by 24 % and 79 % post-therapy, respectively. The interval between last inhaled treatment and bronchoscopy was 3 days.

CONCLUSIONS

Inhaled Azacitidine resulted in negligible plasma levels compared to the previously reported subcutaneous administration and was well-tolerated. The results justify the continued development of inhaled Azacitidine at non-cytotoxic doses for patients with lung-confined malignant and/or premalignant lesions.

5-Azacytidine inhaled dry powder formulation profoundly improves pharmacokinetics and efficacy for lung cancer therapy through genome reprogramming

Background

Epigenetic therapy through demethylation of 5-methylcytosine has been largely ineffective in treating lung cancer, most likely due to poor tissue distribution with oral or subcutaneous delivery of drugs such as 5-azacytidine (5AZA). An inhalable, stable dry powder formulation of 5AZA was developed.

Methods

Pharmacokinetics of inhaled dry powder and aqueous formulations of 5AZA were compared to an injected formulation. Efficacy studies and effect of therapy on the epigenome were conducted in an orthotopic rat lung cancer model for inhaled formulations.

Results

Inhaled dry powder 5AZA showed superior pharmacokinetic properties in lung, liver, brain and blood compared to the injected formulation and for all tissues except lung compared to an inhaled aqueous formulation. Only dry powder 5AZA was detected in brain (~4-h half-life). Inhaled dry powder was superior to inhaled aqueous 5AZA in reducing tumour burden 70–95%. Superiority of inhaled 5AZA dry powder was linked to effectively reprogramming the cancer genome through demethylation and gene expression changes in cancer signalling and immune pathways.

Conclusions

These findings could lead to widespread use of this drug as the first inhaled dry powder therapeutic for treating local and metastatic lung cancer, for adjuvant therapy, and in combination with immunotherapy to improve patient survival.

OAS-RNase L innate immune pathway mediates the cytotoxicity of a DNA-demethylating drug

Drugs that cause epigenetic modification of DNA, such as 5-azacytidine (AZA), are used clinically to treat myelodysplastic syndromes and acute myeloid leukemia. In addition, AZA is being investigated for use against a range of different types of solid tumors, including lung and colorectal cancers. Treatment with AZA causes demethylation of DNA, thus increasing RNA synthesis, including the synthesis of double-stranded RNA, which is otherwise produced in virus-infected cells. We determined that cell death in response to AZA requires the antiviral enzyme RNase L. The results identify a drug target for enhancing the anticancer activity and reducing the toxicity of AZA and related drugs.

Drugs that reverse epigenetic silencing, such as the DNA methyltransferase inhibitor (DNMTi) 5-azacytidine (AZA), have profound effects on transcription and tumor cell survival. AZA is an approved drug for myelodysplastic syndromes and acute myeloid leukemia, and is under investigation for different solid malignant tumors. AZA treatment generates self, double-stranded RNA (dsRNA), transcribed from hypomethylated repetitive elements. Self dsRNA accumulation in DNMTi-treated cells leads to type I IFN production and IFN-stimulated gene expression. Here we report that cell death in response to AZA treatment occurs through the 2′,5′-oligoadenylate synthetase (OAS)-RNase L pathway. OASs are IFN-induced enzymes that synthesize the RNase L activator 2-5A in response to dsRNA. Cells deficient in RNase L or OAS1 to 3 are highly resistant to AZA, as are wild-type cells treated with a small-molecule inhibitor of RNase L. A small-molecule inhibitor of c-Jun NH₂-terminal kinases (JNKs) also antagonizes RNase L-dependent cell death in response to AZA, consistent with a role for JNK in RNase L-induced apoptosis. In contrast, the rates of AZA-induced and RNase L-dependent cell death were increased by transfection of 2-5A, by deficiencies in ADAR1 (which edits and destabilizes dsRNA), PDE12 or AKAP7 (which degrade 2-5A), or by ionizing radiation (which induces IFN-dependent signaling). Finally, OAS1 expression correlates with AZA sensitivity in the NCI-60 set of tumor cell lines, suggesting that the level of OAS1 can be a biomarker for predicting AZA sensitivity of tumor cells. These studies may eventually lead to pharmacologic strategies for regulating the antitumor activity and toxicity of AZA and related drugs.

Low level of 5-Hydroxymethylcytosine predicts poor prognosis in non-small cell lung cancer

The loss of 5-hydroxymethylcytosine (5-hmC) has previously been demonstrated to be implicated in the initiation and progression of various tumors. However, its role in non-small cell lung cancer (NSCLC) remains unknown. The present study aimed to determine the level of 5-hmC in NSCLC and their adjacent normal lung tissues by immunohistochemistry and dot-blot analysis; then the relationship between 5-hmC level and the clinicopathological features of NSCLC and the prognostic significance of 5-hmC level in NSCLC patients were analyzed. By employing the dot-blot analysis, a significant reduction of 5-hmC level in NSCLC tissues compared with the adjacent normal tissues was detected, which were further verified by the immunohistochemistry results on tissue microarrays. Further analyses demonstrated that 65.38% (136/208) presented with low 5-hmC level, and low 5-hmC level was significantly associated with lymph node metastasis (P<0.001), histological type (P<0.001) and large tumor size (P=0.031). Notably, the 5-year overall survival rate of patients with low 5-hmC levels were significantly lower than patients with high 5-hmC levels (P<0.001). In addition, it was demonstrated that 5-hmC level was identified as independent prognostic factor in patients' overall survival. In conclusion, downregulation of 5-hmC may serve as a useful biomarker for NSCLC prognosis evaluation.

The challenges for cancer chemoprevention

The incidence of cancer is rising in parallel with an ageing populous thus increasing the strain on both treatment options and budgets for healthcare providers worldwide. New cancer therapies are being developed but at what cost? The new treatments are expensive and poor survival rates still exist for some cancers. What is needed now is to prevent or at least limit the disease occurring in the first place. This review evaluates the current situation and the progress in upcoming strategies as well as suggesting some areas for further research within the increasingly important field of cancer chemoprevention. The key principles of cancer chemoprevention are discussed and areas for improvement highlighted. Despite significant progress, chemoprevention has not been widely adopted. Cancer chemoprevention has many challenges to face but this only emphasises the size of the task. These hurdles include a lack of awareness of the benefits, a lack of interest and a lack of investment in taking prevention forward. Despite the huge potential importance of cancer prevention and clinical success stories such as the well-publicised HPV vaccine, the challenges remain significant. With cancer and its treatment being a global issue, the opportunities offered by chemoprevention must be re-evaluated and uptake of chemoprevention actively encouraged. If chemoprevention is to be adopted successfully, a holistic approach is required. This approach will involve multidisciplinary teams of healthcare providers and scientists with the big challenge particularly for medicinal chemists being to design and synthesise the ideal chemopreventative agent.

Toxicity and Pharmacokinetic Studies of Aerosolized Clinical Grade Azacitidine

BACKGROUND

Azacitidine as an effective epigenetic therapeutic agent has not been used as an aerosol form to treat lung cancer patients. We aerosolized clinical grade azacitidine (Aza), optimized the formulation, and studied its pharmacokinetics and toxicity in mice.

METHODS

Extrusion-precipitation method and DNA methyltransferase inhibition rate were used to measure the aerodynamic size and aerosolized Aza activity. In the single dose pharmacokinetic study, Aza concentrations in peripheral blood and lungs were measured by LC-MS method. In the multiple-dose toxicity studies, histo-pathological evaluation was used to determine the organ and bone marrow toxicities.

RESULTS

In pharmacokinetic study, aerosolized Aza was found to deposit mainly into the lung with very little drug detected in the circulation. In contrast, intravenously injected (IV) Aza resulted in a high Aza concentration in the peripheral blood, with trace amounts of drug in the lung, and it was associated with significant myelosuppression. No significant myelosuppression, pulmonary toxicity, hepatotoxicity, or nephrotoxicity were observed at a daily dose of 2.5 mg/m(2) for 7 days. Reversible lung inflammation was found in mice treated with 7.5 mg/m(2) aerosolized Aza at 3 but not 6 weeks after treatment.

CONCLUSIONS

Aerosol Aza aerodynamic size favors deposition of the drug to the human lower airways. The aerosol process do not compromise the drug activity. Aerosolized Aza has higher lung deposition and much less systemic toxicity than IV drug. The safe starting dose for clinical phase I trials should be 2.5 mg/m(2) for 5 to 7 days.