Association of time-varying clearance of nivolumab with disease dynamics and its implications on exposure response analysis.

Nivolumab is a human monoclonal antibody that blocks the interaction between PD-1 programmed death-1 (PD-1) and its ligands, PD-L1 and PD-L2. Nivolumab demonstrated efficacy in clinical trials for various types of cancer. A time-varying clearance was identified for nivolumab. We show that the change of clearance over time is associated with the post-treatment effects: clearance decreases when disease status improves. This interaction between posttreatment effects and drug exposure may lead to a biased steep estimate of the exposure-response (E-R) relationship for efficacy. Under this scenario, simulations were performed to develop a proposed methodology to assess the causal effect of drug exposure upon clinical response. Data from nivolumab trials were subsequently used to verify the proposed methodology for E-R analysis. The results showed that E-R analysis results based on pharmacokinetic (PK) metrics derived from the first dose are more consistent with the true E-R or dose-response relationship than the steady-state PK metrics.

Mice infected with Schistosoma mansoni develop a novel non-T-lymphocyte suppressor population which inhibits virus-specific CTL induction via a soluble factor.

We previously observed that Schistosoma mansoni-infected mice were deficient in their ability to mount a CTL response to unrelated viral antigens and to clear a vaccinia viral infection. Here, we explore the mechanism of that deficiency. Mixing experiments showed that splenocytes from S. mansoni-infected mice actively suppress stimulation in vitro of both viral-peptide specific CTL in spleen cells from virus-infected mice, and allospecific CTL. The mechanism of suppression involves at least in part a soluble factor, in that it can occur across a 0.4-microm membrane which prohibits direct cell contact. However, the inhibition is not alleviated by blocking with antibodies to IL-4, IL-10 or TGF-beta. Fractionation of the splenocyte population from S. mansoni-infected mice shows that the suppression is mediated by a non-B, non-T cell that expresses CD16 and Mac-1, but not FcepsilonR or NK1.1. This represents a novel suppressor population that is distinct from the FcepsilonRI(+) populations of non-B, non-T cells in the spleens of S. mansoni-infected mice that provide a major source of IL-4 in these animals. Similar cells in schistosome-infected humans could affect susceptibility to other infections or responsiveness to vaccines.

The combination of zidovudine and interferon alpha-2B in the treatment of adult T-cell leukemia/lymphoma.

Adult T-cell leukemia/lymphoma (ATL) is frequently a very aggressive malignancy with a poor survival despite aggressive multiagent chemotherapy. The combination of the antiretroviral drug zidovudine (AZT) and interferon alpha (IFNalpha) has been reported to induce remissions in patients with ATL. The purpose of this study was to evaluate the clinical response and toxicity following administration of a combination of IFNalpha-2b and AZT in patients with human T-cell lymphotropic virus type I (HTLV-I)-associated ATL. Eighteen patients with ATL (chronic. crisis, acute or lymphoma type) were treated with the combination of AZT (50 - 200 mg orally 5 times a day) and IFNalpha-2b (2.5 - 10 million units subcutaneously daily). Three patients had objective responses lasting more than one month. One patient had a clinical complete remission, lasting 21.6 months and two patients had partial remissions lasting 3.7 and 26.5 months. Six patients were not considered evaluable for response due to short and/or interrupted periods of treatment. Seventeen patients have died with a median survival time after initiation of therapy of 6 months. Neutropenia and thrombocytopenia were the dose limiting toxicities. In conclusion, the response rate in this study was lower than noted in the two previous published series. This may be due to the amount and type of prior treatment our patients had received.

Development of a clinical-scale method for generation of dendritic cells from PBMC for use in cancer immunotherapy.

BACKGROUND: There is growing interest in the use of dendritic cells (DCs) for treatment of malignancy and infectious disease. Our goal was to develop a clinical scale method to prepare autologous DCs for cancer clinical trials. METHODS: PBMC were collected from normal donors or cancer patients by automated leukapheresis, purified by counterflow centrifugal elutriation and placed into culture in polystyrene flasks at 1 x 10(6) cells/mL for 5-7 days at 37 degrees C, with 5% CO(2), with IL-4 and GM-CSF. Conditions investigated included media formulation, supplementation with heat in activated allogeneic AB serum or autologous plasma and time to harvest (Day 5 or Day 7). DCs were evaluated for morphology, quantitative yield, viability, phenotype and function, including mixed leukocyte response and recall response to tetanus toxoid and influenza virus. RESULTS: DCs with a typical immature phenotype (CD14-negative, CD1a-positive, mannose receptor-positive, CD80-positive, CD83-negative) were generated most consistently in RPMI 1640 supplemented with 10% allogeneic AB serum or 10% autologous plasma. Cell yield was higher at Day 5 than Day 7, without detectable differences in phenotype or function. In pediatric sarcoma patients, autologous DCs had enhanced function compared with monocytes from which they were generated. In this patient group, starting with 8.0 +/- 3.7 x 10(8) fresh or cryopreserved autologous monocytes, DC yield was 2.1 +/- 1.0 x 10(8) cells, or 29% of the starting monocyte number. DISCUSSION: In the optimized clinical-scale method, purified peripheral monocytes are cultured for 5 days in flasks at 1 x 10(6) cells/mL in RPMI 1640, 10% allogeneic AB serum or autologous plasma, IL-4 and GM-CSF. This method avoids the use of FBS and results in immature DCs suitable for clinical trials.

Oncogenic mutations in ras create HLA-A2.1 binding peptides but affect their extracellular antigen processing.

Point mutations in oncogene products such as ras may create neoantigenic determinants recognizable by T lymphocytes as tumor antigens, that could be marshalled to eliminate a tumor by inducing specific cytotoxic T lymphocytes (CTL) with an appropriate vaccine. Peptide-pulsed dendritic cells are a promising new approach to cancer vaccines. For such an approach to work, the determinant must be appropriately processed to the right size fragment and be presented by an appropriate HLA molecule. We have investigated both of these issues for a series of ras codon 12 and 13 point mutations that contain sequences predicted to bind to HLA-A2.1, the most common class I HLA molecule. We find that not only do the different mutations affect binding to HLA-A2.1, but also they affect extracellular antigen processing in two ways: by influencing the trimming of flanking residues from the longer sequence and by influencing the susceptibility of the optimal decamer to further proteolytic degradation. The influence of internal residues on cleavage of flanking residues downstream demonstrates the importance of distant interactions between separated amino acid side chains and/or conformational effects in determining antigen processing. These results may be important in designing an effective vaccine to induce mutant ras-specific tumor immunity.

Simultaneous chronic lymphocytic leukemia and chronic myelogenous leukemia. Evidence of a separate stem cell origin.

The authors studied a patient with the simultaneous occurrence of chronic lymphocytic leukemia (CLL) and chronic myelogenous leukemia (CML). The coexistence of these two hematologic malignancies leads to questions about their cell of origin. Through analysis of this patient's DNA, the authors studied the derivation of the two malignancies. They separated the blood into a myeloid-rich fraction and a fraction containing the malignant lymphocytes. JH and bcr probes were used to study these loci in the myeloid and lymphoid fractions and in unfractionated white blood cells. The authors found that the unfractionated leukocytes contained the bcr and JH rearrangements. Conversely, the lymphoid fraction contained only the JH rearrangement, and the myeloid fraction contained only the bcr rearrangement, suggesting that these malignancies arose from separate stem cells. This is the first reported patient with simultaneously occurring CML and CLL definitively shown to arise from distinct progenitors, and this report raises questions about the origin of these two cell lines.

Combined antitumor therapy with the chemotherapeutic drug doxorubicin and an anti-transferrin receptor immunotoxin: in vitro and in vivo studies.

We have determined the in vitro and in vivo efficacy of the combination of doxorubicin and an anti-transferrin receptor-monoclonal antibody (MAb)-ricin A chain immunotoxin. These agents both possess antineoplastic activity and their differing mechanisms of action and toxicities suggest that they may work well in combination. In vitro cytotoxicity was assayed by the inhibition of both 3H-leucine and 3H-thymidine incorporation into H-MESO-1 human malignant mesothelioma cells. In vivo, tumoricidal activity was determined by the effect of treatment on the survival of nude mice bearing H-MESO-1 as an intraperitoneal xenograft. The effect of doxorubicin on the antitumor activity of immunotoxin was directly compared to that of monensin, a well-described immunotoxin potentiator. The coincubation of doxorubicin (1 microM) with immunotoxin in vitro produced no increase in cytotoxicity or rate of cell kill when compared to immunotoxin alone. The addition of monensin to immunotoxin produced a significant increase in both cytotoxicity and the rate of cell kill. In animal trials, all treated groups demonstrated a significant increase in median survival when compared to controls. Treatment with doxorubicin or immunotoxin produced a mean survival time (MST) of 22 and 23 days, respectively, vs. control MST of 10 days. The combination of immunotoxin and doxorubicin increased the MST to 31 days (p = 0.004 vs immunotoxin or doxorubicin alone). Immunotoxin combined with monensin emulsion produced an increase in survival equivalent to doxorubicin/immunotoxin. The use of all three agents produced an additional improvement in survival. Combinations of standard chemotherapeutic drugs and ricin A chain immunotoxins may have additive antitumor effects in the therapy of solid tumors.

Human antibody response to the intravenous and intraperitoneal administration of the F(ab')2 fragment of the OC125 murine monoclonal antibody.

We have characterized the human immune response against murine monoclonal antibodies (HAMA) in 18 patients following administration of the F(ab')2 fragment of the murine monoclonal antibody OC125. OC125 is directed against the CA125 antigen, present on the surface of many human ovarian cancers. An affinity matrix was used to separate serum into immunoglobulin-containing and immunoglobulin-free fractions. HAMA titer was determined on the immunoglobulin fraction with an OC125 sandwich enzyme-linked immunosorbent assay (ELISA). All patients developed an HAMA response, despite the use of F(ab')2 fragments and small amounts (1-4 mg) of antibody. It may be that the intraperitoneal (i.p.) route provides a more marked HAMA response. Enzyme-linked sandwich immunoassays were also used to determine anti-isotype and anti-idiotype titers. Anti-isotype titers were analyzed with antigen irrelevant, isotype-matched murine antibodies and OC125-HRPO. Anti-idiotypes titers were assessed in a sandwich assay that utilized F(ab')2 and F(ab') fragments of OC125. The anti-isotype response tended to be of low titer and short duration, while the anti-idiotype response was of high titer and remarkably persistent. HAMA interfered in an unpredictable manner with the correct measurement of serum levels of CA125 in an enzyme immunoassay using OC125. Corrected values of CA125 could be obtained by measurement of antigen in the immunoglobulin-free fraction of serum. The response of one patient, who developed a markedly elevated anti-idiotype titer after serial i.v./i.p. injections, was further characterized and found to contain an antibody consistent with an anti-anti-idiotype to the CA125 antigen.