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Aim: Imetelstat, a 13-mer oligonucleotide with a lipid tail is being evaluated for treating hematologic myeloid malignancies. This report describes the development of extraction and quantification methods for imetelstat. Methodology & results: Imetelstat was extracted using SPE (rat plasma) or by hybridization using a biotinylated capture probe (human plasma) and was quantified by LC-MS/MS. Calibration curves were established (0.1-50 μg/ml). Stability of imetelstat in plasma was demonstrated. Concentrations of imetelstat extracted using either of the methods and quantified with LC-MS/MS were comparable with a validated ELISA. Conclusion: Two extraction methods (solid phase and hybridization) were developed for quantifying imetelstat in plasma using LC-MS/MS. The hybridization extraction in combination with LC-MS/MS is a novel extraction approach. In recent years, oligonucleotide drugs (ODNs) have gained popularity owing to their ability to target specific genes and provide specificity. ODNs comprise an oligonucleotide sequence, containing 10-50 nucleotides [1,2]. Numerous ODNs have been investigated so far [1][2][3][4]. But only six ODNs (fomivirsen, pegaptanib, mipomersen, eteplirsen, nusinersen and defibrotide sodium) have been approved by the US FDA since 1998 [5].Pharmaceutical development of ODNs has several technical challenges such as maintaining in vivo stability, ensuring delivery and bioavailability, and minimizing off-target effects. These challenges can be minimized by chemical modifications of ODNs to enhance their pharmacokinetic and pharmacodynamic properties [4,6]. These chemical modifications include: sulfurization of the phosphodiester bond to avert degradation by enlindogenous exonucleases, addition of methoxy or methoxyethyl groups to sugar moieties [7,8], locked and unlocked nucleic acids, and alterations in the internucleotide linkage (e.g., amide linkage) resulting in peptide nucleic acids [1]. Sulfurization results in phosphorothioate analogs that are more hydrophobic, exhibit more complex secondary structures with higher protein binding and greater accumulation in organs than phosphodiester analogs [9][10][11].Imetelstat is a novel, first-in-class telomerase inhibitor ODN [12], being investigated for the treatment of hematologic myeloid malignancies [13,14] and certain solid tumors [12,15,16]. Imetelstat is a 13-mer oligonucleotide N3 -P5 thio-phosphoramidate (NPS) with a covalently linked C16 (palmitoyl) lipid moiety at the 5 -end (Figure 1; Supplementary Table 1). Addition of a lipid chain and the modified oligonucleotide backbone enables imetelstat to penetrate cells and tissues, with high biodistribution into normal and malignant cells [12].Imetelstat differs from antisense oligonucleotides in its mechanism of action. Imetelstat is complementary to the template region of the RNA component of telomerase, to which it binds with high affinity and specificity, and directly competes with telomere binding, thereby inhibiting telomerase activity [17]. Thus, imetelstat acts as a classical ac...

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Introduction: Constitutive activation of the classical nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-κB) pathway is a clear driver of B-cell lymphomas, especially the aggressive activated B-cell (ABC) subtype of diffuse large B-cell lymphoma (DLBCL). Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is a key mediator of the classical NF-κB signaling pathway downstream of B-cell receptor and T-cell receptor. MALT1 possesses 2 functions: a scaffolding function to recruit NF-κB signaling proteins and a protease function to cleave and inactivate inhibitors of the NF-κB signaling pathway. Methods: Using a high-throughput screen followed by iterative structure-activity relationship (SAR) analyses, the MALT1 inhibitor JNJ-67856633 was identified. The lead compound was evaluated using biochemical, in vitro cellular and in vivo tumor efficacy and safety models. Results: JNJ-67856633 is a potent, selective, allosteric inhibitor of MALT1 protease activity as measured by biochemical assays or downstream cellular cytokine readouts (IL 6/10) or direct MALT1 substrate cleavage (RelB, BCL10). The compound inhibits proliferation of activated B-cell diffuse large B-cell lymphoma (ABC-DLBCL) cell lines bearing CD79b or CARD11 mutations as well as models mimicking resistance to covalent Bruton's Tyrosine Kinase (BTK) inhibitors. Furthermore, combination effects were observed in CD79b cellular ABC-DLBCL models when JNJ-67856633 was combined with a BTK inhibitor. JNJ-67856633 leads to potent in vivo pharmacodynamic shutdown in CD79b- as well as CARD11-mutant ABC-DLBCL models as measured by serum IL10 or uncleaved BCL10 levels in tumors. JNJ-67856633 exhibits potent tumor growth inhibition in two human DLBCL xenograft models, OCI Ly3 and OCI Ly10, and mutation selection patient derived DLBCL xenografts. To address the role of MALT1 inhibition in T cells, primary human T cells derived from normal healthy volunteers were treated with JNJ-67856633 in vitro. Dose dependent inhibition of the generation of Tregs (CD4+CD25+FoxP3+) following CD3/28 stimulation was observed upon treatment with JNJ-67856633 suggesting a potential immune modulatory role of MALT1 inhibition. Conclusions: Phase 1 clinical trials assessing the safety and efficacy of JNJ-67856633 initiated in 2019. JNJ-67856633 is a combination partner for BTK inhibitors and a promising treatment option for BTKi-resistant tumors, with demonstrated preclinical activity in CARD11 mutant tumors. In addition to ABC-DLBCL, a MALT1 inhibitor is a promising treatment option for patients with CLL, MCL, WM, and FL whose tumors have been shown to be sensitive to inhibition of BTK. MALT lymphomas, characterized by MALT1 and BCL10 translocation, represent another attractive target for MALT1 inhibition. Citation Format: Ulrike Philippar, Tianbao Lu, Nele Vloemans, Mariette Bekkers, Luc Van Nuffel, Marcello Gaudiano, Katarzyna Wnuk-Lipinska, Bas-jan Van Der Leede, Katie Amssoms, Kristof Kimpe, Bart Medaer, Tony Greway, Yann Abraham, Max Cummings, Emanuele Trella, Greet Vanhoof, Weimei Sun, Jan Willem Thuring, Peter Connolly, Jan Linders, Haopeng Rui, Sriram Balasubramanian, Amy Johnson, John Gerecitano, Jenna Goldberg, James P. Edwards, Yusri Elsayed, Jennifer Smit, Jaqueline Bussolari, Jaqueline Bussolari, Ricardo Attar. Discovery of JNJ-67856633: A novel, first-in-class MALT1 protease inhibitor for the treatment of B cell lymphomas [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5690.

Imetelstat, a 13-base oligonucleotide (59-TAGGGTTAGACAA-39), is a potent, investigational telomerase inhibitor in clinical development for the treatment of hematologic myeloid malignancies. Modifications to imetelstat oligonucleotide chemistry include an N39-P59 thio-phosphoramidate backbone linkage to improve biologic stability and the addition of a palmitoyl tail at the 59-position to enhance cellular membrane permeability. Other oligonucleotides have been previously shown to have in vitro test-system-dependent outcomes when potent cytochrome P450 inhibition in human liver microsomes (HLM) is observed, but such inhibition is not observed in cryopreserved human hepatocytes (CHH). Outcomes in CHH are consistent with clinical reports in which no interactions were reported. In the present study, imetelstat was evaluated for in vitro inhibition of eight P450 enzymes, namely CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 in CHH (0.5 million cells/ml). Assays were performed using validated conditions, including short substrate times (10 minutes), and at the approximate substrate K m concentration. Imetelstat was found to have little to no inhibition of all P450 isoforms evaluated, with inhibitor concentration that causes 50% inhibition (IC 50) values >100 mM. Maximum percent inhibition values for each P450 isoform at 100 mM imetelstat were <20% except for CYP2C8 activity, which was inhibited by 49%. Using a static mechanistic model, the predicted change in area under the curve of a victim drug coadministered with imetelstat was 1.04-fold, projecting no relevant clinical interaction. Overall, the results from this in vitro study suggest that clinical use of imetelstat is unlikely to affect the pharmacokinetics of concomitant therapies that undergo cytochrome P450-mediated metabolism.