Somatostatin receptor 2 (SSTR2) is frequently overexpressed on several types of solid tumors, including neuroendocrine tumors and small-cell lung cancer. Peptide agonists of SSTR2 are rapidly internalized upon binding to the receptor and linking a toxic payload to an SSTR2 agonist is a potential method to kill SSTR2-expressing tumor cells. Herein, we describe our efforts towards an efficacious SSTR2-targeting cytotoxic conjugate; examination of different SSTR2-targeting ligands, conjugation sites, and payloads led to the discovery of 22 (PEN-221), a conjugate consisting of microtubule-targeting agent DM1 linked to the C-terminal side chain of Tyr3–octreotate. PEN-221 demonstrates in vitro activity which is both potent (IC50 = 10 nM) and receptor-dependent (IC50 shifts 90-fold upon receptor blockade). PEN-221 targets high levels of DM1 to SSTR2-expressing xenograft tumors, which has led to tumor regressions in several SSTR2-expressing xenograft mouse models. The safety and efficacy of PEN-221 is currently under evaluation in human clinical trials.

Small cell lung cancer (SCLC) is an aggressive neuroendocrine carcinoma with a 95% mortality rate with no improvement to treatment in decades, and new therapies are desperately needed. PEN-221 is a miniaturized peptide-drug conjugate ($2 kDa) designed to target SCLC via a Somatostatin Receptor 2 (SSTR2)-targeting ligand and to overcome the high proliferation rate characteristic of this disease by using the potent cytotoxic payload, DM1. SSTR2 is an ideal target for a drug conjugate, as it is overexpressed in SCLC with limited normal tissue expression. In vitro, PEN-221 treatment of SSTR2-positive cells resulted in PEN-221 internalization and receptor-dependent inhibition of cellular proliferation. In vivo, PEN-221 exhibited rapid accumulation in SSTR2-positive SCLC xenograft tumors with quick clearance from plasma. Tumor accumulation was sustained, resulting in durable pharmacodynamic changes throughout the tumor, as evidenced by increases in the mitotic marker of G 2-M arrest, phosphohistone H3, and increases in the apoptotic marker, cleaved caspase-3. PEN-221 treatment resulted in significant antitumor activity, including complete regressions in SSTR2positive SCLC xenograft mouse models. Treatment was effective using a variety of dosing schedules and at doses below the MTD, suggesting flexibility of dosing schedule and potential for a large therapeutic window in the clinic. The unique attributes of the miniaturized drug conjugate allowed for deep tumor penetration and limited plasma exposure that may enable long-term dosing, resulting in durable tumor control. Collectively, these data suggest potential for antitumor activity of PEN-221 in patients with SSTR2-positive SCLC.

Polyomavirus T antigens share a common N-terminal sequence that comprises a DnaJ domain. DnaJ domains activate DnaK molecular chaperones. The functions of J domains have primarily been tested by mutation of their conserved HPD residues. Here, we report detailed mutagenesis of the polyomavirus J domain in both large T (63 mutants) and middle T (51 mutants) backgrounds. As expected, some J mutants were defective in binding DnaK (Hsc70); other mutants retained the ability to bind Hsc70 but were defective in stimulating its ATPase activity. Moreover, the J domain behaves differently in large T and middle T. A given mutation was twice as likely to render large T unstable as it was to affect middle T stability. This apparently arose from middle T's ability to bind stabilizing proteins such as protein phosphatase 2A (PP2A), since introduction of a second mutation preventing PP2A binding rendered some middle T J-domain mutants unstable. In large T, the HPD residues are critical for Rb-dependent effects on the host cell. Residues Q32, A33, Y34, H49, M52, and N56 within helix 2 and helix 3 of the large T J domain were also found to be required for Rb-dependent transactivation. Cyclin A promoter assays showed that J domain function also contributes to large T transactivation that is independent of Rb. Single point mutations in middle T were generally without effect. However, residue Q37 is critical for middle T's ability to form active signaling complexes. The Q37A middle T mutant was defective in association with pp60 c-src and in transformation.Polyomavirus T antigens function both in replication of the virus and in transformation of the host cell. Large T is central to virus production as the initiator of viral DNA replication (20). Middle T and small T also play important roles in different aspects of polyomavirus infection (21,23,55). Defects in viral DNA replication and transcription, as well as defects in viral assembly, have been observed in different mutants of middle T and small T (1,7,8,22,38). Each of the viral early proteins also contributes to regulation of host cell function. Large T is able to immortalize primary cells (44), to block differentiation (37), and to provoke apoptosis (18, 48). These activities are mediated via association with the retinoblastoma susceptibility (Rb) family of tumor suppressors. Middle T, the major transforming protein, works through activation of cellular signaling pathways that are regulated by src-family tyrosine phosphorylation (15). Small T is able to promote cell cycle progression via association with protein phosphatase 2A (PP2A) (39).All three T antigens are produced by differential splicing of common primary transcripts (56). As a result, they have the identical N-terminal sequence of 79 amino acids that encompasses a DnaJ domain. DnaJ domains, consisting of approximately 70 amino acids, have a helical structure in which a conserved HPD motif is found between helix 2 and helix 3 (2, 13, 32, 43, 54). DnaJ domains, found in a broad range of proteins, function to stimulate ...

SummaryBackground Existing treatments for asthma are not effective in all patients and disease exacerbations are common, highlighting the need for increased understanding of disease mechanisms and novel treatment strategies. The leukotriene pathway including the enzyme responsible for arachidonic acid release from cellular phospholipids, cPLA 2 a, is a major contributor to asthmatic responses and an attractive target in asthma therapies. Objective The study reported here investigates (a) the differential effects of in vitro exposure of peripheral blood mononuclear cells (PBMCs) to allergen between asthma and healthy subjects, and (b) the contribution of cPLA 2 a to these differences in gene expression. Methods In vitro responses of asthma (N = 26) and healthy (N = 11) subject PBMC samples to allergen stimulation in the presence and absence of cPLA 2 a inhibition or 5-lipoxygenase inhibition were compared at the gene expression level using oligonucleotide arrays and at the protein level using ELISA. Results Subject samples within both asthma and healthy groups showed allergen-dependent cytokine production and allergen-dependent gene expression changes, although transcriptional profiling identified 153 genes that were modulated significantly differently by allergen between asthma and healthy subjects. Among these were genes previously associated with asthma, but the majority (about 80%) have not previously been associated with asthma. Conclusions Transcriptional profiling elucidated novel gene expression differences between the asthmatic and healthy subject samples. Although 5-lipoxygenase inhibition did not significantly affect allergen-modulated gene expression, the inhibition of cPLA 2 a activity affected many of the allergen-dependent, asthma-associated gene expression changes.

Middle T antigen (MT) is the principal oncoprotein of murine polyomavirus. Experiments on the acute immediate effects of MT expression on cellular RNA levels showed that expression of osteopontin (OPN) was strongly induced by MT expression. Osteopontin is a protein known to be associated with cancer. It has a role in tumor progression and invasion. Protein analysis confirmed that MT induced the secretion of OPN into the extracellular medium. Expression of antisense OPN RNA had no effect on the growth of MT-transformed cells. However, it had a strong effect on the ability of MT transformants to migrate or to fill a wound. Analysis of MT mutants implicated both the SHC and phosphatidylinositol 3-kinase pathways in OPN induction. Reporter assays showed that MT regulated the OPN promoter through two of its PEA3 (polyoma enhancer activator 3) sites. As critical PEA3 sites are also part of the polyomavirus enhancer, the same signaling important for viral replication also contributes to virally induced metastatic potential.Murine polyomavirus causes a broad range of tumors in various types of cells and has been a valuable model for studying growth regulation (21,29,33). Middle T antigen (MT) is the principal oncoprotein of polyomavirus that is necessary (9, 79) and often sufficient (81) for transformation in vitro. MT delivered as a transgene or a retrovirus can induce tumors in a wide variety of tissues (5,38,55,78,104). Viruses carrying mutant MTs often are defective for transformation in vitro or tumorigenesis in vivo (7,18,35,100). Similarly, transgenic mutant MTs show different phenotypes from the wild type (96).MT is associated with membranes and underlying cytoskeletal elements (2,46,69,75). Its ability to transform depends upon that association (9). MT functions as a kind of adaptor, on which cellular signaling proteins are assembled. It binds the A and C subunits of protein phosphatase 2A (63, 90). As a result of this association, MT is able to bind protein tyrosine kinases of the SRC family (SRC, YES, and FYN) (15,17,42,52). In the protein tyrosine kinase complex, MT is phosphorylated on three major tyrosine residues: 315, 322, and 250 (10,39,44,68). Each of these sites represents a connection to a signal generator: 315 to phosphatidylinositol 3-kinase (PI3K) and one or more additional interacting proteins (41, 49, 97), 250 to SHC (8, 24) and thence to GRB2 and SOS, and 322 to phospholipase C-␥1 (PLC-␥1) (77) and potentially PI3K as well. Mutation of amino acid 322 has had a modest effect in some transformation assays (57), but there is a striking effect at low serum concentration (77). Mutation of tyrosine 250 has a dramatic effect on MT transforming ability (57), as do mutations in the regions amino terminal to position 250 (the NPTY motif) (27,28). Tyrosine 250 represents part of the binding site for the adaptor SHC, and that binding leads to tyrosine phosphorylation of SHC (8, 24). In turn, SHC binding and tyrosine phosphorylation are responsible for the recruitment of GRB2. Association with PI3K is profo...

Platinum drugs have proven to be effective in treating cancer, for example >90% of men with testicular cancer are cured with a platinum therapeutic. Platinum drugs are also widely used for the adjuvant treatment of common cancers such as those of the lung, colon and ovary. However for the majority of tumor types the clinical response rates for platinum therapies are low, for example the 1 year survival rate for lung cancer patients treated with platinum therapeutics is ∼30%. The key limitations of the existing platinum therapies are the dose limiting toxicities that restrict dose and/or duration of therapy and the absence of personalization that targets the drugs to the patients most likely to benefit. To address these issues we have designed a novel prodrug of cisplatin, BTP-114. On infusion into the blood a maleimide group on BTP-114 covalently attaches to serum albumin. This prolongs the circulation of BTP-114 in plasma and alters the biodistribution of the compound. Importantly the dose of platinum can be increased and the amount of platinum that accumulated in xenograft tumor tissue and the amount of platinum bound to tumor DNA are both increased relative to cisplatin. An elevation of DNA damage in tumor cells in vivo is observed with BTP-114. Together the properties of BTP-114 result in pronounced and sustained tumor growth inhibition compared to cisplatin. In parallel to the discovery of BTP-114 we have explored potential biomarkers to predict which tumors are most likely to respond. These data will be presented towards developing BTP-114 as a personalized platinum medicine for cancer patients. BM and RA contributed equally to this work. Citation Format: Benoit Moreau, Rossitza Alargova, Adam Brockman, Kerry Whalen, Jamie Quinn, Kristan Meetze, Patrick Bazinet, Michelle DuPont, Beata Krawiec, Kristina Kriksciukaite, Charles Lemelin, Patrick LimSoo, Haley Oller, Mike Ramstack, Danielle Rockwood, Rajesh Shinde, Sukhjeet Singh, Brian White, Tsun AuYeung, Craig Dunbar, Mark Bilodeau, Richard Wooster. BTP-114: An albumin binding cisplatin prodrug with improved and sustained tumor growth inhibition. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4484. doi:10.1158/1538-7445.AM2015-4484

The specific targeting of cytotoxic drugs to solid tumors has achieved success with the advent of antibody drug conjugates (ADCs). This approach has had notable success but has also met with limitations. The most common issue limiting ADC effectiveness is believed to be low tumor permeation by these large (∼150 kDa) molecules. Attempts to address this limitation have been focused on the design of miniaturized biologic drug conjugates such as those with small protein or small molecule targeting moieties. However, these efforts uniformly result in conjugates with poor pharmacokinetics in contrast to the extended plasma pharmacokinetics observed with ADCs. The Pentarin platform encapsulates miniaturized biological drug conjugates within nanoparticles to improve the biodistribution of these classes of conjugates. There are multiple benefits to this strategy. Through the enhanced permeability and retention (EPR) effect the nanoparticles accumulate in the perivascular space of the tumor tissue. Next the nanoparticles release the permeable miniaturized conjugate that can penetrate in to the tumor, bind to an over-expressed target on the cancer cell surface, internalize the payload and elicit a strong biological effect. All of this is further enhanced by the extended plasma pharmacokinetics of the nanoparticle when compared to the conjugate alone. To exemplify the Pentarin platform we have designed novel miniaturized biologic drug conjugates to an over-expressed target found in small cell lung cancer. In vitro data has shown the designed conjugates specifically and potently target tumor cells expressing the receptor of interest. When encapsulated in nanoparticles, these miniaturized biologic drug conjugates have improved plasma pharmacokinetics, the amount of payload delivered to xenograft tumors is increased and the xenograft efficacy is significantly more pronounced over drug conjugate not in a nanoparticle. These observations correlate with in vivo mechanistic assays in the xenograft tissue. These data will be presented, together with the name of the target, to demonstrate the impact of the Pentarin platform and to show progress towards the first clinical candidate from this work. Citation Format: Mark T. Bilodeau, Rajesh Shinde, Brian White, Patrick Bazinet, Kerry Whalen, Michelle Dupont, Kristina Kriksciukaite, Jamie Quinn, Beata Sweryda-Krawiec, Rossitza Alargova, Adam Brockman, Patrick Lim Soo, Kristan Meetze, Benoit Moreau, Haley Oller, Mike Ramstack, Danielle Rockwood, Sukhjeet Singh, Tsun Au Yeung, Sudha Kadiyala, Craig Dunbar, Richard Wooster. Pentarins: Improved tumor targeting through nanoparticle encapsulation of miniaturized biologic drug conjugates. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3674. doi:10.1158/1538-7445.AM2015-3674

The field of immuno-oncology has revolutionized cancer patient care and improved survival and quality of life for patients. Much of the focus in the field has been on exploiting the power of the adaptive immune response through therapeutic targeting of T cells. While these approaches have markedly advanced the field, some challenges remain, and the clinical benefit of T cell therapies does not extend to all patients or tumor indications. Alternative strategies, such as engaging the innate immune system, have become an intense area of focus in the field. In particular, the engagement of natural killer (NK) cells as potent effectors of the innate immune response has emerged as a promising modality in immunotherapy. Here, we review therapeutic approaches for selective engagement of NK cells for cancer therapy, with a particular focus on targeting the key activating receptors NK Group 2D (NKG2D) and cluster of differentiation 16A (CD16A).