indotecan (LMP400)

Patient-derived GBM cells and isogenic PTEN-null and PTEN-WT glioma cells were treated with LMP400 (Indotecan), a novel non-camptothecin TOP1 inhibitor alone and in combination with a PARP inhibitor, Olaparib or Niraparib. Animal studies confirmed both an anti-glioma effect and sufficient BBB penetration to prolong survival of mice treated with the drug combination. Our findings provide a proof of concept for the combined treatment with LMP400 and Niraparib in a subset of GBM patients with PTEN deficiency.

We show that the BETi OTX015 synergized with the new class of synthetic noncamptothecin TOP1i, LMP400 (indotecan), to block tumor growth in aggressive CRPC xenograft models. Consistent with this observation, TOP1 was highly expressed in metastatic CRPC (mCRPC) and its expression correlated with the expression of BET family genes-BRD4, BRD3 and BRD2. These studies open new avenues for the rational combinatorial treatment of aggressive PCa-particularly, cancers refractory to androgen signaling inhibitors.

CONCLUSION LMP400 and Niraparib act synergistically to target PTEN-deficient glioblastoma by inducing DNA damage and cell death. These results will be further verified in isogenic cells in vitro as well as in vivo in a mouse model driven by PTEN deletion which would strongly support a novel therapeutic strategy in a subset of glioblastoma with PTEN loss.

To identify synthetic lethal therapeutic targets to overcome chemoresistance in SLFN11 deficient cells, we performed a genome-wide RNAi screen with the human druggable genome siRNA library by using camptothecin (CPT), a TOP1 inhibitor, in SLFN11 wild-type (WT) and knock-out (KO) prostate cancer DU145 cells...Treatment with non-toxic-doses of M4344 and SRA737 reversed drug resistance of the SLFN11 KO cells to TOP1 inhibitors [CPT, and clinically used topotecan and LMP400 (indotecan)]...We also confirmed synergy with ATR/CHK1 inhibitors in combination of other clinical DNA-damaging agents (TOP2 inhibitor: etoposide, alkylating agent: cisplatin, and PARP inhibitor: talazoparib)...Co-treatment with ATR inhibitor and CPT resulted in G2/M arrest and apoptotic cell death, and formation of micronuclei and fragmented nuclei in SLFN11 KO cells, compared with SLFN11 WT cells. Collectively, our results provide a new therapeutic rationale for the clinical development of combination treatments of chemotherapeutic DNA-targeted agents with ATR/CHK1 inhibitors based on SLFN11 status.

In addition, the combination of irinotecan and the ataxia telangiectasia and Rad3-related protein (ATR) inhibitor VE-822 was tested in SLFN11-negative PDXs, and two clinical non-camptothecin TOP1 inhibitors (LMP400 and LMP776) were tested. In conclusion, a substantial proportion of TNBC respond to irinotecan. BRCAness, high SLFN11 expression, and RB1 loss are highly predictive of response to irinotecan and the clinical indenoisoquinoline TOP1 inhibitors.