MLN0128, a Potential Target Therapy for Myeloid Proliferation Neoplasia (MPN) with a Benefit of Prolonging Survival

MLN0128 (TAK-228, INK128) is an investigational new drug (IND) that is currently being evaluated in clinical trials and has showed promising efficacies in patients with solid cancer. MLN0128 is one of the second generation of inhibitors for mammalian target of rapamycin (mTORi), which suppresses the dysregulated cell survival signaling activities in cancer cells by specifically inhibiting both mTORC1 and mTORC2 in PI3K/mTOR pathway. MLN0128 was reported inhibiting acute myeloid leukemia (AML) stem cells and progenitors [Zeng et al, Oncotarget, 2016]. However, it is yet to be clarified whether MLN0128 can improve survival time in leukemia patients. Here, we report data from the investigation of the impact of MLN0128 on leukemia survival in mice. We tested MLN0128 in a published mouse model which simultaneously produces experimental mice with genotypes that are associated with pediatric leukemia, including myeloproliferative neoplasm (MPN) and juvenile myelomonocytic leukemia (JMML), and adult chronic myelomonocytic leukemia (CMML) [Vara et al, Blood Adv.2020]. Specifically, mice with deletion of Phosphatase and tensin homolog gene (Pten) and loss-of-heterozygosity of Neurofibromin 1 (Nf1) (Pten ^Δ/ΔNf1 ^LOH) develop JMML, mice with Pten deletion and Nf1 heterozygosity (Pten ^Δ/ΔNf1 ^Δ/wt) develop pediatric MPN, both of which cause juvenile death; mice with a single copy of Pten deletion and Nf1 LOH (Pten ^Δ/wtNf1 ^LOH) develop CMML in adulthood. We previously reported that all of those diseased mice shared a feature with elevated activities in PI3K/MAPK/mTOR pathways. We first collected nucleated cells from bone marrow (BM) of the diseased mice and tested the inhibition of MLN0128 on colony formation of hematopoietic progenitors (CFU-GM) at a concentration range of 1-1000nM. Our data demonstrated that MLN028 significantly inhibited the CFU-GM colony formation of BM cells from mice with all three diseased genotypes, in a dose-dependent fashion. Importantly, the IC50 for CFU-GM was less than 100nM, which is in the concentration range of MLN0128 in the blood from patients who orally received MLN0128 at dosage range of 4-12mg/day [Ghobrial et al AJH 2016]. We then investigated the impact of MLN0128 on life span in diseased mice. We administrated MLN0128 in gavage at dosages of 0.5-1μg/g body weight, starting at an age of postnatal day 17-18 (PND17-18), 3-5 times a week, repeated for 5 weeks followed by a pause in 6 ^th week every course. Our data showed that MLN0128 significantly reduced the spleen sizes in treated mice with all diseased genotypes comparing to those treated with vehicle. The survival time was significantly prolonged in MLN0128-treated mice with genotypes of MNP (n=7 vs 3, median 150 vs 102 days) and CMML (n=7 vs 6, median 100 vs 56 days), comparing with the mice treated by vehicle. Unfortunately, we did not observe a survival improvement in treated JMML mice, but substantially swollen kidneys were found in the dead JMML mice, which was likely due to tumor-lysis syndrome because JMML mice carried a significantly worse leukemic burden. In conclusion, our data demonstrate that MLN0128 can significantly inhibit colony formation of BM cells from mice with genotypes of JMML, MPN, and CMML; and MLN0128 can significantly expand survival time of mice with genotypes of MPN and CMML, which has never been reported in previous studies that were related to mTORi in pediatric leukemia. Our data suggest that MLN0128 may be a potential target therapy for pediatric MPN and CMML with a benefit of prolonging survival. Further investigation is ongoing to evaluate the potential of MLN0128 in improving survival of JMML mice after minimizing the tumor-lysis syndrome by tipping down MLN0128 dosage.