ALBERT

Description: Inorganic arsenics like arsenic trioxide (ATO) are novel anti-cancer drugs active in acute promyelocytic leukemia (APL) and multiple myeloma (MM). ATO induces apoptosis of plasma cells by several mechanisms including down-regulation of BCL-2 expression and inhibition of DNA-binding by NF-κB. The amount of ATO that can be safely given is low because of QTc-prolongation. ZIO-101, a new organic arsenic, is in phase-1/-2 trials. ZIO-101 can be safely given at much higher doses than ATO. We evaluated the in vivo anti-myeloma activity of ZIO-101 in a SCID-hu mouse model of human myeloma. LAGλ-1 was developed from a person with melphalan-resistant and LAGλ-1B from a person with bortezomib-resistant myeloma. Each severe combined immunodeficient (SCID) mouse was implanted with a 2–4 mm3 fragment of LAGλ-1B or LAGλ-1 into the left superficial gluteal muscle. Fragments were allowed to grow for 14 d when human IgG was first detectable. ZIO-101 was given IV 1 or 2 times/d using three different schedules: one day/w, 3 days/w or 5 days/w at doses of 50– 200 mg/kg/d. Tumor volume and human IgG were assessed weekly. Doses up to 200 mg/kg were well-tolerated. Anti-myeloma effects were observed in both models at doses of 100 – 200 mg/kg on all 3 schedules. Mice receiving 100 mg/kg twice daily thrice weekly and those receiving 200 mg/kg once weekly showed marked anti-myeloma activity (100 mg/kg, P = 0.03; 200 mg/kg, P = 0.001) and reduced human IgG levels (100 mg/kg, P 〈 0.001; 200 mg/kg, P = 0.01) compared to controls. We are evaluating ZIO-101 in other SCID-hu models of human myeloma and exploring different doses and schedules of ZIO-101 alone or combined with other anti-myeloma agents. In summary, these data show activity of ZIO-101 in human myeloma in vivo. These studies provide the bases for future clinical trials.

Description: CD40 is a TNF receptor found on the cell surface of mature B cells (B lymphocytes) and most B-cell malignancies including multiple myeloma (MM). SGN-40 is a high-affinity, humanized monoclonal antibody that targets the CD40 antigen. Recently, it has been shown that SGN-40 decreases the proliferation of malignant B cells by partial agonistic signaling and effector functions in vitro. In this study, we examined the anti-MM effects of SGN-40 in vivo using a CD40+ SCID-hu murine model of human myeloma, LAGκ-1A. Each immunodeficient (SCID) mouse was implanted with a 2.0 – 4.0 mm3 LAGκ-1A tumor fragment into the left hind limb muscle. The tumor was allowed to grow for 14 days at which time human IgG levels were detectable in the mouse serum. Mice were then randomly assigned to one of four SGN-40 treatment groups (6 mice per treatment group). SGN-40 was administered via intraperitoneal injection twice per week at doses of 0.1, 0.3, 1, and 3 mg/kg. Control mice were given a control IgG antibody (3 mg/kg) using the same schedule. Mice receiving the higher doses of SGN-40 showed marked inhibition of tumor growth (0.3 mg/kg, P 〈 0.02; 1 mg/kg, P 〈 0.03; and 3 mg/kg, P 〈 0.04) and reduction of paraprotein levels (1 mg/kg, P 〈 0.05; and 3 mg/kg, P 〈 0.03) compared to mice receiving control antibody. At the lowest dose of SGN-40 evaluated (0.1 mg/kg) a slight inhibition of tumor growth was observable, but there was no effect on human paraprotein. Treatment with SGN-40 was not associated with any observed toxicity. Based on these data with SGN-40 monotherapy, we are currently investigating the antitumor activity of SGN-40 plus bortezomib as well as other available anti-MM agents using our in vivo SCID-hu myeloma murine model. These data for single-agent SGN-40 are encouraging and support testing SGN-40 both alone and in combination regimens to treat MM patients.

Description: Histone deacetylase (HDAC) inhibitors represent a new mechanistic class of anti-cancer therapeutics that inhibit HDAC enzymes and have been shown to have anti-proliferative effects in cancer cells (including drug resistance subtypes), induce apoptosis, inhibit angiogenesis, and sensitize cancer cells when combined with other available anti-cancer therapies. PXD101 is a novel investigational small molecule drug that selectively inhibits HDAC enzymes. In recent preclinical studies, PXD101 has been shown to have the potential to treat a wide range of solid and hematological malignancies either as a monotherapy or in combination with other active agents. In this study, we evaluated the activity of PXD101 on multiple myeloma samples when used as monotherapy or in combination with the proteasome inhibitor bortezomib. In vitro experiments indicated that PXD101 pretreatment (20 mM; 3h) sensitized RPMI-8226 human multiple myeloma cells to subsequent bortezomib exposure (5 nM; 72h). To examine PXD101 and bortezomib in vivo, two mouse models of human multiple myeloma were utilized (LAGλ-1 and LAGκ-1B). LAGλ-1 was generated from a patient resistant to melphalan therapy and LAGκ-1B from a patient who progressed on bortezomib treatment (Campbell et al, International Journal of Oncology 2006). SCID mice were implanted with LAGλ-1 or LAGκ-1B tumor fragments into the left superficial gluteal muscle. Tumors were allowed to grow for 14 days at which time human IgG levels were detectable in the mouse serum, and mice were randomly assigned into treatment groups. Groups consisted of Vehicle only, PXD101 alone (40 mg/kg), bortezomib alone (0.5 mg/kg), or PXD101 (40 mg/kg) + bortezomib (0.5 mg/kg). In one cohort, PXD101 and bortezomib were administered twice weekly (M, Th) and in another cohort PXD101 was administered 5 days a week (M-F) and bortezomib twice weekly (M, Th). When administered, PXD101 was given i.p twice daily and bortezomib once daily intravenously. The results of these animal experiments will provide preclinical information on the activity of PXD101 monotherapy and PXD101/bortezomib combination therapy on drug-resistant myeloma samples, and may help to define the optimal schedule for potential clinical evaluation of this drug combination.

Description: The peripheral benzodiazepine receptor (mPBR) appears to be a potential target to induce apoptosis in tumor cells. The expression of this receptor has been linked to a poor prognosis in cancer patients. PK11195 may represent a new, well-tolerated potent chemosensitizing agent that affects multiple resistance mechanisms within malignant cells. We have evaluated whether PK11195 inhibits multiple myeloma (MM) cell growth in vitro; and, furthermore, whether this drug can chemosensitize a melphalan resistant human MM tumor, LAGλ-1 (Campbell et al, International Journal of Oncology 2006), to arsenic trioxide (ATO) and melphalan using an in vivo SCID-hu model. The MM cell lines RPMI8226 and U266 were treated with varying concentrations of PK11195 (1 – 100 mM). After incubating with PK11195 for 24 hours, cell growth was measured by MTT assay. Those cells treated with PK11195 showed decreased proliferation at concentrations as low as 1 mM compared to the untreated cells. Next, we investigated the chemosensitizing effects of PK11195 using an in vivo model of human MM. To accomplish this, each immunodeficient (SCID) mouse was implanted with a 2.0 – 4.0 mm3 LAGλ-1 tumor fragment into the left superficial gluteal muscle. The tumors were allowed to grow for 14 days at which time human IgG levels were detectable in the mouse serum or when tumors became palpable (21 days) and mice were blindly assigned into treatment groups. PK11195 (10, 50 and 100 mg/kg) was administered via oral gavage once weekly when combined with melphalan and once daily five times per week when combined with ATO. Melphalan (3 mg/kg) was administered once weekly via intraperitoneal (i.p.) injection. ATO (1.25 mg/kg) was administered once daily five times per week via i.p. injection. Mice receiving the combination of PK11195 and melphalan (3 mg/kg) showed marked inhibition of tumor growth (PK11195 10 mg/kg, P = 0.03; PK11195 50 mg/kg, P = 0.02; PK11195 200 mg/kg, P 〈 0.01) compared to mice receiving no therapy. Animals treated with melphalan, as a single agent, did show minimal tumor growth inhibition and reduced paraprotein levels whereas mice treated with single agent PK11195 showed tumor growth similar to the control mice. Mice receiving the combination of PK11195 and low dose ATO (1.25 mg/kg) also showed inhibition of tumor growth (PK11195 200 mg/kg, P 〈 0.01) whereas treatment with either single agent PK11195 or ATO demonstrated growth similar to the control groups. Treatment with the highest dose of PK11195 (200 mg/kg) was not associated with any observed toxicity suggesting that high doses can be safely administered and are well tolerated. In this study, we showed PK11195 inhibits MM cell growth in vitro at very low concentrations and can chemosensitize drug resistant tumor cells in vivo at doses that have no observable toxicity. We are further evaluating PK11195 as a single agent and in combination therapy both in vitro and in vivo..

Description: Vascular endothelial growth factor (VEGF) is an important signaling protein that plays a critical role in vasculogenesis and angiogenesis, and serves as one of the contributors to physiological or pathological conditions that can stimulate the formation of new blood vessels. The uncontrolled growth of new blood vessels is an important contributor to a number of pathological conditions, including multiple myeloma (MM). In support of this, bone marrow angiogenesis has been shown to correlate with disease status and poor prognosis in MM. VEGF also directly induces myeloma cell proliferation. Based on these findings, we evaluated a new mouse/human anti-VEGF antibody using our SCID-hu mouse models of human MM. Each immunodeficient (SCID) mouse was implanted with a 2.0 – 4.0 mm3 LAGκ-1A tumor fragment into the left superficial gluteal muscle. The tumors were allowed to grow for 14 days at which time human IgG levels were detectable in the mouse serum, and mice were blindly assigned into one of two treatment groups. In one group, anti-VEGF antibody was administered via intraperitoneal injection twice per week at a dose of 5 mg/kg. In the other cohort, control mice were given a control IgG antibody (5 mg/kg) on the same schedule. Mice receiving the anti-VEGF antibody showed marked inhibition of tumor growth (P = 0.0005) and reduction of paraprotein levels (P = 0.0002) compared to mice receiving control antibody. On day 42, LAGκ-1A-bearing mice receiving the anti-VEGF antibody showed a 70% reduction in human paraprotein levels and an 80% decrease in tumor volume compared the control antibody treated animals. Treatment with the anti-VEGF antibody was not associated with any observed toxicity. We are currently evaluating this anti-VEGF antibody in several of our mouse models of human MM and plasma cell leukemia. Based on these data with anti-VEGF monotherapy, we are currently investigating the anti-tumor activity of anti-VEGF antibody plus bortezomib as well as other available anti-MM agents using our in vivo SCID-hu myeloma murine models. Preliminary results are encouraging with single agent anti-VEGF antibody and additional studies may be used to direct the clinical development of anti-VEGF antibody treatment alone and in combination regimens for patients with relapsing or refractory MM.