Michael N. Petrus

Phase 1 trial of IL-15 trans presentation blockade using humanized Mik-Beta-1 mAb in patients with T-cell large granular lymphocytic leukemia

In the present study, Hu-Mikβ1, a humanized mAb directed at the shared IL-2/IL-15Rβ subunit (CD122) was evaluated in patients with T-cell large granular lymphocytic (T-LGL) leukemia. Hu-Mikβ1 blocked the trans presentation of IL-15 to T cells expressing IL-2/IL-15Rβ and the common γ-chain (CD132), but did not block IL-15 action in cells that expressed the heterotrimeric IL-15 receptor in cis. There was no significant toxicity associated with Hu-Mikβ1 administration in patients with T-LGL leukemia, but no major clinical responses were observed. One patient who had previously received murine Mikβ1 developed a measurable Ab response to the infused Ab. Nevertheless, the safety profile of this first in-human study of the humanized mAb to IL-2/IL-15Rβ (CD122) supports its evaluation in disorders such as refractory celiac disease, in which IL-15 and its receptor have been proposed to play a critical role in the pathogenesis and maintenance of disease activity.

Phase I trial of IL-15 transpresentation blockade using humanized Mik-Beta-1 monoclonal antibody in patients with T-cell large granular lymphocytic leukemia

In the present study, Hu-Mikβ1, a humanized mAb directed at the shared IL-2/IL-15Rβ subunit (CD122) was evaluated in patients with T-cell large granular lymphocytic (T-LGL) leukemia. Hu-Mikβ1 blocked the trans presentation of IL-15 to T cells expressing IL-2/IL-15Rβ and the common γ-chain (CD132), but did not block IL-15 action in cells that expressed the heterotrimeric IL-15 receptor in cis. There was no significant toxicity associated with Hu-Mikβ1 administration in patients with T-LGL leukemia, but no major clinical responses were observed. One patient who had previously received murine Mikβ1 developed a measurable Ab response to the infused Ab. Nevertheless, the safety profile of this first in-human study of the humanized mAb to IL-2/IL-15Rβ (CD122) supports its evaluation in disorders such as refractory celiac disease, in which IL-15 and its receptor have been proposed to play a critical role in the pathogenesis and maintenance of disease activity.

Selective targeting of JAK/STAT signaling is potentiated by Bcl-xL blockade in IL-2–dependent adult T-cell leukemia

Significance Adult T-cell leukemia (ATL) is caused by the human T-cell lymphotropic virus-1 (HTLV-1). Presently there is no curative therapy for ATL. In the leukemic cells, the HTLV-1–encoded protein Tax (transactivator from the X-gene region) activates disordered interleukin expression, which triggers JAK/STAT signaling. The HTLV-1–encoded protein Tax also induces the expression of the antiapoptotic protein Bcl-xL (B-cell lymphoma-extra large). In the present study, the combination of the JAK inhibitor ruxolitinib and the Bcl-2/Bcl-xL inhibitor navitoclax provided additive/synergistic antitumor efficacy in IL-2–dependent ATL cell lines and in a mouse model of human ATL as well as with ex vivo peripheral blood mononuclear cells (PBMCs) from ATL patients compared with either drug alone, supporting a therapeutic trial of this combination in patients with ATL. Adult T-cell leukemia (ATL) develops in individuals infected with human T-cell lymphotropic virus-1 (HTLV-1). Presently there is no curative therapy for ATL. HTLV-1–encoded protein Tax (transactivator from the X-gene region) up-regulates Bcl-xL (B-cell lymphoma-extra large) expression and activates interleukin-2 (IL-2), IL-9, and IL-15 autocrine/paracrine systems, resulting in amplified JAK/STAT signaling. Inhibition of JAK signaling reduces cytokine-dependent ex vivo proliferation of peripheral blood mononuclear cells (PBMCs) from ATL patients in smoldering/chronic stages. Currently, two JAK inhibitors are approved for human use. In this study, we examined activity of multiple JAK inhibitors in ATL cell lines. The selective JAK inhibitor ruxolitinib was examined in a high-throughput matrix screen combined with >450 potential therapeutic agents, and Bcl-2/Bcl-xL inhibitor navitoclax was identified as a strong candidate for multicomponent therapy. The combination was noted to strongly activate BAX (Bcl-2-associated X protein), effect mitochondrial depolarization, and increase caspase 3/7 activities that lead to cleavage of PARP (poly ADP ribose polymerase) and Mcl-1 (myeloid cell leukemia 1). Ruxolitinib and navitoclax independently demonstrated modest antitumor efficacy, whereas the combination dramatically lowered tumor burden and prolonged survival in an ATL murine model. This combination strongly blocked ex vivo proliferation of five ATL patients’ PBMCs. These studies provide support for a therapeutic trial in patients with smoldering/chronic ATL using a drug combination that inhibits JAK signaling and antiapoptotic protein Bcl-xL.

Development of an IL-15–autocrine CD8 T-cell leukemia in IL-15–transgenic mice requires the cis expression of IL-15Rα

IL-15 has growth-promoting effects on select lymphoid subsets, including natural killer (NK) cells, NK T cells, intraepithelial lymphocytes (IELs), CD8 T cells, and γδ-T cells. Constitutive expression of murine IL-15 in IL-15-transgenic mice was reported to cause T-NK leukemia. We investigated whether IL-15 expression is sufficient for leukemic transformation using a human IL-15-transgenic (IL-15Tg) mouse model. We noted that 100% of the mice observed over a 2-year period (n > 150) developed fatal expansions of CD8 T cells with NK markers, and determined that these cells expressed IL-15 receptor alpha (IL-15Rα). The expression of IL-15Rα on CD8 T cells appears to be required for uncontrolled aggressive lymphoproliferation, because none of the IL-15Rα(-/-)-IL-15Tg mice that we followed for more than 2 years developed the fatal disease despite controlled expansion of CD8 T cells. In addition, in contrast to IL-15Tg mice, in which leukemia-like CD8 T cells expressed IL-15Rα persistently, acutely activated normal CD8 T cells only transiently expressed IL-15Rα. Inhibition of DNA methylation enabled sustained IL-15Rα expression induced by activation. We present a scenario for IL-15Tg mice in which CD8 T cells that acquire constitutive persistent IL-15Rα expression are at a selective advantage and become founder cells, outgrow other lymphocytes, and lead to the establishment of a leukemia-like condition.

Augmented efficacy of brentuximab vedotin combined with ruxolitinib and/or Navitoclax in a murine model of human Hodgkin’s lymphoma

Significance Hodgkin’s lymphoma (HL) manifests activation of Janus kinase (JAK)/ signal transducer and activator of transcription (STAT) signaling pathway and CD30 expression on Reed–Sternberg cells. Additivity/synergy inhibiting effects were noted with combination treatments in vitro with HL cell line, HDLM-2, when treated with JAK 1/2 inhibitor; ruxolitinib with B-cell lymphoma 2 (Bcl-2)/B-cell lymphoma-extra large) (Bcl-xL) inhibitor, Navitoclax; or with anti-CD30 toxin conjugate, brentuximab vedotin (BV). Either ruxolitinib combined with Navitoclax or BV alone prolonged survival period but did not cure HDLM-2 tumor-bearing mice whereas BV combined with ruxolitinib and/or with Navitoclax resulted in sustained complete remissions in this model of HL. These studies provide scientific support for clinical trials to evaluate BV combined with ruxolitinib in select patients with HL. Despite relative success of therapy for Hodgkin’s lymphoma (HL), novel therapeutic agents are needed for patients with refractory or relapsed disease. Recently, anti-PD1 immunotherapy or treatment with the anti-CD30 toxin conjugate brentuximab vedotin (BV) have been associated with remissions; however, the median responses of complete responses (CRs) with the latter were only 6.7 mo. To obtain curative therapy, other effective agents, based on HL biology, would have to be given in combination with BV. Hodgkin’s Reed–Sternberg (HRS) cells secrete cytokines including IL-6 and -13, leading to constitutive activation of JAK/STAT signaling. In the present study the JAK1/2 inhibitor ruxolitinib reduced phosphorylation of STAT3 and STAT6 and expression of c-Myc in the HL cell line HDLM-2. These changes were enhanced when, on the basis of a matrix screen of drug combinations, ruxolitinib was combined with the Bcl-2/Bcl-xL inhibitor Navitoclax. The combination augmented expression of Bik, Puma, and Bax, and attenuated Bcl-xL expression and the phosphorylation of Bad. The use of the two-agent combination of either ruxolitinib or Navitoclax with BV or the three-agent combination strongly activated Bax and increased activities of cytochrome c and caspase-9 and -3 that, in turn, led to cleavage of poly(ADP ribose) polymerase and Mcl-1. Either ruxolitinib combined with Navitoclax or BV alone prolonged survival but did not cure HDLM-2 tumor-bearing mice, whereas BV combined with ruxolitinib and/or with Navitoclax resulted in a sustained, complete elimination of the HDLM-2 HL. These studies provide scientific support for a clinical trial to evaluate BV combined with ruxolitinib in select patients with HL.

Augmented efficacy with the combination of blockade of the Notch-1 pathway, bortezomib and romidepsin in a murine MT-1 adult T-cell leukemia model

Adult T-cell leukemia (ATL) is an aggressive malignancy caused by human T-cell lymphotropic virus-1. There is no accepted curative therapy for ATL. We have reported that certain ATL patients have increased Notch-1 signaling along with constitutive activation of the nuclear factor-κB pathway. Physical and functional interaction between these two pathways provides the rationale to combine the γ-secretase inhibitor compound E with the proteasome inhibitor bortezomib. Moreover, romidepsin, a histone deacetylase inhibitor, has demonstrated major antitumor action in leukemia/lymphoma. In this study, we investigated the therapeutic efficacy of the single agents and the combination of these agents in a murine model of human ATL, the MT-1 model. Single and double agents inhibited tumor growth as monitored by tumor size (P<0.05), and prolonged survival of leukemia-bearing mice (P<0.05) compared with the control group. The combination of three agents significantly enhanced the antitumor efficacy as assessed by tumor size, tumor markers in the serum (human soluble interleukin-2 receptor-α and β2-microglobulin) and survival of the MT-1 tumor-bearing mice, compared with all other treatment groups (P<0.05). Improved therapeutic efficacy obtained by combining compound E, bortezomib and romidepsin supports a clinical trial of this combination in the treatment of ATL.

Cytokine receptor signaling is required for the survival of ALK− anaplastic large cell lymphoma, even in the presence of JAK1/STAT3 mutations

Significance Activating Janus kinase (JAK) mutations occur only in a minority of T-cell malignancies, which would appear to limit the clinical application of JAK inhibition for these diseases. Our study suggests that targeting JAK might be of value in treating diverse forms of anaplastic lymphoma kinase (ALK)− anaplastic large cell lymphoma (ALCL). Most exogenous cytokine-independent ALK− ALCL cells of diverse origins responded to JAK inhibition regardless of JAK mutation status. The JAK inhibitor sensitivity of these cells correlated with their positive signal transducer and activator of transcription 3 (STAT3) phosphorylation status. Using retroviral shRNA knockdown, we showed that all JAK inhibitor-sensitive cells were dependent on JAK1/STAT3 for survival. Cytokine receptor signaling and gain-of-function JAK1/STAT3 mutations contribute to JAK1/STAT3 dependency. Our data suggest that JAK inhibition maybe a rational therapy for patients with phosphorylated STAT3+ ALK− ALCL. Activating Janus kinase (JAK) and signal transducer and activator of transcription (STAT) mutations have been discovered in many T-cell malignancies, including anaplastic lymphoma kinase (ALK)− anaplastic large cell lymphomas (ALCLs). However, such mutations occur in a minority of patients. To investigate the clinical application of targeting JAK for ALK− ALCL, we treated ALK− cell lines of various histological origins with JAK inhibitors. Interestingly, most exogenous cytokine-independent cell lines responded to JAK inhibition regardless of JAK mutation status. JAK inhibitor sensitivity correlated with the STAT3 phosphorylation status of tumor cells. Using retroviral shRNA knockdown, we have demonstrated that these JAK inhibitor-sensitive cells are dependent on both JAK1 and STAT3 for survival. JAK1 and STAT3 gain-of-function mutations were found in some, but not all, JAK inhibitor-sensitive cells. Moreover, the mutations alone cannot explain the JAK1/STAT3 dependency, given that wild-type JAK1 or STAT3 was sufficient to promote cell survival in the cells that had either JAK1or STAT3 mutations. To investigate whether other mechanisms were involved, we knocked down upstream receptors GP130 or IL-2Rγ. Knockdown of GP130 or IL-2Rγ induced cell death in selected JAK inhibitor-sensitive cells. High expression levels of cytokines, including IL-6, were demonstrated in cell lines as well as in primary ALK− ALCL tumors. Finally, ruxolitinib, a JAK1/2 inhibitor, was effective in vivo in a xenograft ALK− ALCL model. Our data suggest that cytokine receptor signaling is required for tumor cell survival in diverse forms of ALK− ALCL, even in the presence of JAK1/STAT3 mutations. Therefore, JAK inhibitor therapy might benefit patients with ALK− ALCL who are phosphorylated STAT3+.

Chimeric antigen receptor modified T cells that target chemokine receptor CCR4 as a therapeutic modality for T‐cell malignancies

With the emerging success of treating CD19 expressing B cell malignancies with ex vivo modified, autologous T cells that express CD19‐directed chimeric antigen receptors (CAR), there is intense interest in expanding this evolving technology to develop effective modalities to treat other malignancies including solid tumors. Exploiting this approach to develop a therapeutic modality for T cell malignancies for which the available regimens are neither curative, nor confer long term survival we generated a lentivirus‐based CAR gene transfer system to target the chemokine receptor CCR4 that is over‐expressed in a spectrum of T cell malignancies as well as in CD4+CD25+Foxp3+T regulatory cells that accumulate in the tumor microenvironment constituting a barrier against anti‐tumor immunity. Ex vivo modified, donor‐derived T cells that expressed CCR4 directed CAR displayed antigen‐dependent potent cytotoxicity against patient‐derived cell lines representing ATL, CTCL, ALCL and a subset of HDL. Furthermore, these CAR T cells also eradicated leukemia in a mouse xenograft model of ATL illustrating the potential utility of this modality in the treatment of a wide spectrum of T cell malignancies.

A new domain in the Toll/IL-1R domain-containing adaptor inducing interferon-β factor protein amino terminus is important for tumor necrosis factor-α receptor-associated factor 3 association, protein stabilization and interferon signaling.

Toll/IL-1R domain-containing adaptor inducing interferon-ß (IFN-ß) factor (TRIF) is a key adaptor for Toll-like receptor (TLR) 3 and TLR4 signaling. Using a novel cDNA isolate encoding a TRIF protein with a 21-residue deletion (Δ160-181) from its amino-terminal half, we investigated the impact of this deletion on TRIF functions. Transfection studies consistently showed higher expression levels of the (Δ160-181) TRIF compared to wild-type (wt) TRIF, an effect unrelated to apoptosis, cell lines or plasmid amplification. Colocalization of wt and (Δ160-181) TRIF proteins led to a dramatic reduction of their respective expressions, suggesting that wt/(Δ160-181) TRIF heterocomplexes are targeted for degradation. We demonstrated that wt TRIF associates with tumor necrosis factor-a receptor-associated factor 3 (TRAF3) better than (Δ160-181) TRIF, culminating in its greater ubiquitination and proteolysis. This explains, in part, the differential expression levels of the two TRIF proteins. Despite higher expression levels in transfected cells, (Δ160-181) TRIF inefficiently transactivated the IFN pathway, whereas the nuclear factor-κB (NF-κB) pathway activation remained similar to that by wt TRIF. In coexpression studies, (Δ160-181) TRIF marginally contributed to the IFN pathway activation, but still enhanced NF-κB signaling with wt TRIF. Therefore, this 21 amino acid sequence is crucial for TRAF3 association, modulation of TRIF stability and activation of the IFN pathway.

Selective targeting of JAK/STAT signaling is potentiated by Bcl-xL blockade in IL-2-dependent adult T-cell leukemia.

Adult T-cell leukemia (ATL) develops in individuals infected with human T-cell lymphotropic virus-1 (HTLV-1). Presently there is no curative therapy for ATL. The HTLV-1-encoded protein Tax up-regulates Bcl-xL expression and constitutively activates interleukin-2 (IL-2), IL-9, and IL-15 autocrine/paracrine systems resulting in amplified JAK/STAT signaling. Consequently, inhibition of JAK signaling reduces ex vivo proliferation of PBMCs from ATL patients in smoldering and chronic stages. Currently, two JAK inhibitors are approved for human use. In this study, we examined activity of multiple JAK inhibitors in IL-2-dependent and IL-2-independent ATL cell lines. The highly selective JAK inhibitor ruxolitinib was examined in a high-throughput matrix screen and the Bcl-2/Bcl-xL inhibitor navitoclax was identified as a strong candidate for multicomponent therapy. An examination of the mechanistic underpinnings of this combination highlighted a stimulation of Bim and PUMA expression and reduced phosphorylation of BAD upon cellular exposure to ruxolitinib. The combination was noted to strongly activate BAX, effect mitochondrial depolarization and increase caspase 3/7 activity that leads to PARP and Mcl-1 cleavage. Ruxolitinib and navitoclax independently demonstrated modest antitumor efficacy while the combination dramatically lowered tumor burden and prolonged survival in an aggressive ATL murine model. Critically, this combination strongly blocked ex vivo proliferation of five ATL patients’ PBMCs. These studies provide support for a therapeutic trial in patients with smoldering and chronic ATL using a drug combination that inhibits JAK signaling and anti-apoptotic protein Bcl-xL.