Objective. The IKK complex regulates NF-B activation, an important pathway implicated in the rheumatoid arthritis (RA) disease process. This study was undertaken to assess the efficacy of N-(6-chloro-7-methoxy-9H-␤-carbolin-8-yl)-2-methylnicotinamide (ML120B), a potent and selective small molecule inhibitor of IKK␤.Methods. Polyarthritis was induced in rats by injection of Freund's complete adjuvant into the hind footpad. ML120B was administered orally twice daily, either prophylactically or therapeutically. Paw volumes and body weights were measured every 2-3 days throughout the study. We assessed bone erosions by several methods: histologic evaluation, quantitative micro-computed tomography (micro-CT) imaging analysis, and measurement of type I collagen fragments in the serum. Quantitative polymerase chain reaction was used to evaluate expression of messenger RNA for genes related to inflammation and to bone and cartilage integrity.Results. Oral administration of ML120B inhibited paw swelling in a dose-dependent manner (median effective dosage 12 mg/kg twice daily) and offered significant protection against arthritis-induced weight loss as well as cartilage and bone erosion. We were able to directly demonstrate that NF-B activity in arthritic joints was reduced after ML120B administration. Also, we observed that down-regulation of the NF-B pathway via IKK␤ inhibition dampened the chronic inflammatory process associated with rat adjuvant-induced arthritis.Conclusion. The results of the present study suggest that IKK␤ inhibition is an effective therapeutic approach to treat both the inflammation and the bone/ cartilage destruction observed in RA. Methods for the determination of serum markers for bone and cartilage destruction, as well as micro-CT analysis, may aid in predicting and evaluating the therapeutic efficacy of IKK␤ inhibition therapy in humans.

In the present study we have characterized T cell-driven immune function in mice that are genetically deficient in PKC theta. In response to simple immunologic stimulation invoked by in vivo T cell receptor (TCR) cross-linking, these mice showed significantly depressed plasma cytokine levels for IL-2, IL-4, IFNgamma, and TNFalpha compared to wild-type (WT) mice. In parallel, spleen mRNA levels for these cytokines were reduced, and NF-kappaB activation was also reduced in PKC theta knockouts (KO). Injection of allogeneic cells into the footpad of PKC theta deficient mice provoked a significantly diminished local T cell response compared to WT mice similarly challenged. Unlike comparable cells from wild type mice, CD45RBhi T cells harvested from PKC theta deficient mice failed to induce colitis in the SCID-CD45RB cell transfer model of IBD. In another T cell-dependent model of inflammatory disease, PKC theta deficient animals developed far less severe neurologic signs and reduced spinal cord inflammatory cell infiltrate compared to WT controls in the MOG-induced EAE model. A fundamental role for PKC theta in T cell activation and in the development of T cell-mediated inflammatory diseases is indicated by these results.

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.

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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.