Phase 1b study of RGX-202-01, a first-in-class oral inhibitor of the SLC6A8/CKB pathway, in combination with FOLFIRI and bevacizumab (BEV) in second-line advanced colorectal cancer (CRC)

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Background: A proprietary in vivo target discovery screen identified creatine kinase-B (CKB) as a cancer driver in KRAS mutant (KRAS-mut) CRC. CKB promotes tumor growth and survival under hypoxia. CKB generates the energetic metabolite phospho-creatine (PCr), which is imported into cells through the creatine transporter, SLC6A8. PCr generates intracellular ATP that enables tumoral survival. RGX-202-01 is a small molecule inhibitor of SLC6A8 that depletes intracellular PCr and ATP, resulting in apoptosis. In a completed Phase 1a study, RGX-202-01 monotherapy demonstrated objective anti-tumor activity in the relapsed/refractory KRAS-mut CRC setting without dose-limiting toxicity. The objectives of this ongoing Phase 1b study are to evaluate safety, PK/PD, and efficacy of RGX-202-01 in combination with standard-of-care (SOC) FOLFIRI + BEV in second-line CRC, a setting where SOC therapy results in an ORR and mPFS of approximately 15% and 6 months, respectively. Methods: Subjects with advanced CRC who had disease progression after receiving a first line oxaliplatin-containing regimen were eligible. The dose expansion phase of the study was restricted to CKB-expressing CRC tumors. As of 01-14-2022, 16 patients (pts) have been enrolled. 8 pts were enrolled in 2 dose escalation cohorts of RGX-202-01: 2400mg BID (4 pts) and 3000mg BID (4 pts) combined with FOLFIRI and BEV. 8 pts were enrolled in the dose expansion phase of the study and received RGX-202-01 3000mg BID combined with FOLFIRI and BEV Results: No DLTs were observed and the MTD was not reached in the dose escalation phase. Grade 3 TRAEs were observed in 25% of pts. Most common TRAEs were GI in nature. There were no Grade 4-5 TRAEs. PK analysis showed sustained RGX-202-01 drug exposures in both escalation cohorts above target levels (IC50). Serum and urine creatine measurements indicated robust SLC6A8 target inhibition. 9 pts had KRAS-mut CRC, and all were evaluable for RECIST 1.1 response. 4 of these pts had cPR,1 patient had uPR and 4 pts had SD as best response (ORR 56%, DCR 100%). 5 of these pts remain on therapy ranging from 11-54 weeks and a patient with a cPR at 16 weeks followed by surgery with curative intent remains with NED at 24 weeks after surgery. Seven pts had KRAS WT CRC, of which 3 were evaluable (2 pts are pending 1st scan assessment; 2 pts are off study and did not receive 1 full cycle of treatment). Of the 3 KRAS WT evaluable pts, all had SD as best response. 2 were on study for 38 and 24 weeks respectively and 1 is ongoing at 16 weeks. Conclusions: RGX-202-01 combined with FOLFIRI and BEV was well tolerated with no DLTs at the dose levels evaluated which induced potent inhibition of SLC6A8. Antitumor activity was noted in KRAS mutated colorectal cancer, consistent with preferential pre-clinical activity in RAS mutated tumors. Enrollment in the expansion phase continues. Clinical trial information: NCT03597581.

Therapeutic targeting of SLC6A8 creatine transporter suppresses colon cancer progression and modulates human creatine levels

Colorectal cancer (CRC) is a leading cause of cancer mortality. Creatine metabolism was previously shown to critically regulate colon cancer progression. We report that RGX-202, an oral small-molecule SLC6A8 transporter inhibitor, robustly inhibits creatine import in vitro and in vivo, reduces intracellular phosphocreatine and ATP levels, and induces tumor apoptosis. RGX-202 suppressed CRC growth across KRAS wild-type and KRAS mutant xenograft, syngeneic, and patient-derived xenograft (PDX) tumors. Antitumor efficacy correlated with tumoral expression of creatine kinase B. Combining RGX-202 with 5-fluorouracil or the DHODH inhibitor leflunomide caused regressions of multiple colorectal xenograft and PDX tumors of distinct mutational backgrounds. RGX-202 also perturbed creatine metabolism in patients with metastatic CRC in a phase 1 trial, mirroring pharmacodynamic effects on creatine metabolism observed in mice. This is, to our knowledge, the first demonstration of preclinical and human pharmacodynamic activity for creatine metabolism targeting in oncology, thus revealing a critical therapeutic target.

Abstract LB-133: Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors

RGX-104, a first-in-class small-molecule LXR agonist modulates innate immunity and cancer progression via transcriptional activation of ApoE. ApoE protein suppresses tumor cell invasion and angiogenesis, and also depletes circulating and tumoral myeloid derived suppressor cells (MDSC), leading to T cell activation.A multivariate approach was used to address pharmacokinetic (PK) and pharmacodynamic relationships of RGX-104 in a phase 1 dose escalation study in patients with relapsed/refractory solid tumors. The study entailed multiple escalation arms with RGX-104 as monotherapy and in combination with nivolumab, ipilimumab, or docetaxel. Various markers including intratumoral ApoE and its receptor LRP1 in biopsy specimens, gene expression of LXR-targets in whole blood, serum markers including cytokines and lipids, as well as immune cell types such as MDSC, CD8 T-cells, and neutrophils in peripheral blood from patients were monitored at several time points. PK metrics were tracked to assess dose response relationships. Clinical outcomes such as objective response, time to disease progression, and duration on therapy were used for exploratory correlative analyses. A generally dose dependent increase in steady state exposure to RGX-104 was observed among all cohorts; the lowest efficacious exposure among patients with partial response was ~14,000 ng*h/mL. Treatment with RGX-104 at doses ranging from 120 mg BID to 240 mg BID induced expression of LXR targets, ApoE [2.7X (p=0.008) to 7.1X (p=0.007)] and ABCA1 [ 6.3X (p=1.20E-03) to 7X (p=8.1E-04] over baseline in a generally dose-dependent manner as assessed in whole blood. Similarly, MDSC depletion, ranging from 70%-90% relative to baseline, was observed in patients treated with RGX-104 along with concomitant CD8 T-cell activation; similar effects were noted in patients in combination cohorts. A model to explore dose dependency of change in immune cell types suggested that baseline levels of MDSC were most predictive of the magnitude of MDSC reduction after treatment, and that favorable clinical outcomes correlate with the extent of MDSC reduction and T cell activation. Low baseline levels of tumoral ApoE were associated with greater clinical benefit, with almost all patients with stable disease or partial response exhibiting ApoE tumor positive score of ≤20%; these patients also exhibited low/negative PD-L1 (<1%) staining, revealing a target specific tumor biomarker and PD-L1 subset that could support prospective patient selection. These and additional markers will be tracked in expansion cohorts of RGX-104 in combination with pembrolizumab and carboplatin/pemetrexed for 1st line treatment of patients with metastatic non-small cell lung cancer (PD-L1 <1%) and in combination with docetaxel for 2nd line treatment of patients with small cell lung cancer.

Citation Format: Monica Mita, Alan Mita, Erika Hamilton, Gerald S. Falchook, Michael Postow, Bartosz Chmielowski, Russell J. Schilder, James Strauss, Emerson Lim, Shubham Pant, Angela Jain, Oliver Rixe, Rebecca Redman, Kevin B. Kim, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Nimisha Schneider, Renee Deehan, Tobi Guennel, Joe Lin, Sohail Tavazoie, Roger Waltzman, Eric Rowinsky, Michael Szarek, Subhasree Sridhar, Robert Busby, Narayan Lebaka, Celia Andreu, Isabel Kurth, David Darst, Masoud Tavazoie, Syed Raza, Robert Wasserman, Foster C. Gonsalves. Correlative analysis of pharmacokinetics and pharmacodynamics of RGX-104, a first-in-class Liver-X-Receptor (LXR) agonist, and clinical outcomes in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-133.

Abstract CT146: RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts

Background: RGX-104 is a small-molecule LXR agonist that modulates innate immunity via transcriptional activation of the ApoE gene. Binding of ApoE to its receptor LRP8 robustly inhibits angiogenesis and depletes myeloid derived suppressor cells (MDSC), thereby activating cytotoxic T-lymphocytes. MDSCs are associated with resistance to both checkpoint inhibitors (CPI) and chemotherapy, providing a rationale for combination therapy with RGX-104. We previously reported results of the RGX-104 monotherapy dose escalation for which 26 patients with refractory solid tumors were treated in 5 dose cohorts. On-target AEs included hyperlipidemia and neutropenia. Flow-cytometry demonstrated MDSC depletion with associated T cell activation, which correlated with clinical benefit. A 40% disease control rate (DCR; SD+PR) was observed with a confirmed partial response (PR) by irRC (>79% reduction in index lesions) in a patient with platinum-refractory small cell lung cancer (SCLC). Methods: Here, we present the safety, biomarker and efficacy results of the docetaxel combination arm of the RGX-104 trial. Cohort 1- RGX-104 80 mg BID, and docetaxel at 35 mg/m2 days 1, 8, and 15 of a 28-day cycle; Cohort 2- RGX-104 80 mg BID, 5 days-on/2 days-off (5/2), and docetaxel at 28 mg/m2 on above schedule. Cohort 3- RGX-104 100 mg BID (5/2), and docetaxel as per cohort 2. Results: As of February 7, 2020, 11 patients with refractory solid tumors have been treated in 3 dose escalation cohorts with RGX-104 plus docetaxel. AEs were consistent with the individual toxicity profiles of docetaxel and RGX-104, with neutropenia being the most common AE and dose-limiting in cohort 1. The 5/2 dosing regimen in cohorts 2 and 3 resulted in significantly fewer episodes of neutropenia and no DLTs, while maintaining pharmacodynamic effects including >50% sustained MDSC depletion. A 66% DCR was observed in 9 evaluable patients including 2 patients in cohort 2 with PRs, a CPI-refractory SCCHN patient and a CPI-refractory melanoma patient, who remains on treatment at 36 weeks. A patient with melanoma in Cohort 3 had an initial assessment of SD and continues on study at 14 weeks. Clinical responses were associated with increases in T cell activation markers exceeding that generally observed with RGX-104 alone (up to a 5-fold increase in total CD8 T cells, a 7-fold increase in LAG-3+ CD8 T cells, and a 75-fold induction of serum IFNγ). Conclusion: The safety profile and marked pharmacodynamic and clinical activity of the RGX-104/docetaxel combination in CPI-refractory patients supports further development of this regimen. Consequently, the RGX-104/docetaxel regimen will be evaluated in a Phase 1b/2 expansion cohort in patients with relapsed/refractory ES-SCLC/high grade-neuroendocrine tumors.

Citation Format: Emerson Lim, Erika P. Hamilton, Rebecca Redman, Michael A. Postow, Russell J. Schilder, Monica M. Mita, Alain C. Mita, Bartosz Chmielowski, James Strauss, Angela Jain, Shubham Pant, Olivier Rixe, Tomislav Dragovich, R. Donald Harvey, Igor Puzanov, Kevin B. Kim, Eric K. Rowinsky, Michael Szarek, Foster Gonsalves, Isabel Kurth, Celia Andreu, Robert W. Busby, David Darst, Masoud Tavazoie, Syed Raza, Narayan Lebaka16, Robert Wasserman, Gerald Falchook. RGX-104, a first-in-class immunotherapy targeting the liver-X receptor (LXR): Initial results from the phase 1b RGX-104 plus docetaxel combination dose escalation cohorts [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT146.

Abstract CT147: Phase 1 dose escalation of MSC-1, a humanized anti-LIF monoclonal antibody, in patients with advanced solid tumors

Leukemia Inhibitory Factor (LIF) is a pleiotropic cytokine, which is highly expressed in a subset of tumors and correlates with poor prognosis. LIF is hypothesized to contribute to tumor microenvironment immunosuppression and regulation of cancer stem cells. MSC-1 is a first-in-class humanized IgG1 monoclonal antibody that potently and selectively inhibits LIF. In pre-clinical models, MSC-1 decreases tumor growth through inhibition of STAT3 signaling, promoting immune stimulatory macrophages and increasing tumor infiltration of CD8 T and NK cells.

The Phase Ia clinical study employed an accelerated 3 + 3 escalation design to explore safety and tolerability, dose-limiting toxicities (DLTs), preliminary efficacy, define a recommended phase II dose (RP2D), and evaluate exploratory tumor biomarkers. Eligible patients had advanced relapsed/refractory solid tumors and received treatment with MSC-1 intravenously (75mg-1500 mg) once every 3-weeks as a single agent until disease progression. The three highest dose cohorts were expanded to further assess safety, PK, engagement of LIF in the periphery, and assess immuno-regulatory tumor activity in matched pre- and on-treatment tumor biopsies.

Forty-one patients (pts) were enrolled (14 in dose escalation; 27 in expanded cohorts) with the last pt completing the study on September 23, 2019. The most common tumor types were pancreatic (13), colorectal (5), head & neck (4) and ovarian (4). Pts had received a median of 3 prior lines of therapy. All pts experienced at least one adverse event (AE). The most common considered drug-related AEs were fatigue (N=8, 20%) and gastrointestinal disorder (N=8, 20%), and there was 1 considered drug-related SAE (Gr 2 osteonecrosis of jaw in a head and neck cancer patient who previously received radiation to the area and denosumab). There were no Dose Limiting Toxicities observed during the first cycle of treatment and 2 pts discontinued treatment due to AEs.

The PK profile of MSC-1 was linear with an estimated terminal half-life of ∼13 days and benign anti-drug antibody profile. There was evidence of durable peripheral saturation of LIF binding demonstrating high level of target engagement. Results supported the selection of a RP2D of 1500 mg Q3W. Prolonged stable disease (≥ 16 weeks) was observed in 9 pts. Analysis of paired biopsies collected from matched metastatic lesions supported MSC-1 mediated STAT3 signaling inhibition, stimulatory (M1) to suppressive (M2) macrophage skewing in the majority of paired biopsies evaluated and increased CD8 T-cell infiltration in a subset of samples.

Single agent MSC-1 was well tolerated in doses ranged from 75 mg to 1500 mg IV OD in patients with advanced solid tumors, showed promising activity as an anti-cancer therapy, and is Phase 1b/2 ready for combination with other agents. The updated final safety, efficacy, PK, LIF stabilization analyses, and tumor biopsy data will be presented.

Citation Format: Alison Schram, Erkut Borazanci, Irene Brana, Maria Vieito Villar, Elena Garralda, Anna Spreafico, Marc Oliva, Nehal Lakhani, Robert Wasserman, Kimberly Hoffmann, Robin Hallett, Judit Anido, Dorotea Maetzel, Patricia Giblin, Enda Moran, Adrianne Kelly, Joan Seoane, Daniel D. Von Hoff, Lillian Siu, Josep Tabernero. Phase 1 dose escalation of MSC-1, a humanized anti-LIF monoclonal antibody, in patients with advanced solid tumors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT147.

Phase I monotherapy dose escalation of RGX-202, a first-in-class oral inhibitor of the SLC6a8/CKB pathway, in patients with advanced gastrointestinal (GI) solid tumors

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Background: About 65% of advanced colorectal cancer (CRC) patients (pts) have creatine kinase B (CKB) expressing tumors. CKB expressing (CKB+) GI cancer cells import creatine via the creatine transporter SLC6a8 and utilize it to generate intracellular ATP. RGX-202, a small molecule inhibitor of SLC6a8, reduces intracellular creatine and ATP levels, leading to apoptosis. RGX-202 treatment triggers complete tumor regressions in multiple CKB+ preclinical models, including KRAS mutant CRC. Methods: RGX-202-001 is a phase I escalation/expansion study of RGX-202 +/- FOLFIRI in pts with advanced GI tumors. The primary safety objective during dose escalation is to identify the maximum tolerated dose (MTD), or the maximum tested dose at which multiple dose-limiting toxicities (DLTs) are not observed. The primary efficacy objective is to estimate the antitumor activity of RGX-202 by RECIST. Results: As of January 31, 2020, 17 pts have been treated in 4 single agent dose escalation cohorts: 600 mg BID (3 pts), 1200 mg BID (4 pts), 2400mg BID (5 pts) and 3600mg BID (5pts) given continuously. No DLTs were observed and an MTD was not reached. Treatment-related adverse events (TRAEs) occurring in > 2 pts are shown in the Table. There were no Grade 4 TRAEs. At the highest dose, 2 of 3 CRC pts had prolonged disease control: a patient with a KRAS G13D mutant cancer had SD for 14 weeks; and a patient with KRAS G12V mutant (MSS) cancer had a confirmed PR ongoing at 30 weeks. Exposure to RGX-202 was greater than dose-proportional and the average AUC0-24 ranged from ~15,700 ng-hr/mL in cohort 1 to 241,097 ng-hr/mL in in Cohort 4. Serum and urine creatine levels, pharmacodynamic markers of SLC6a8 inhibition, correlated with systemic exposure to RGX-202. Conclusions: Among 17 patients treated with single agent therapy, no DLTs occurred; notably, exposures predicted to be sufficient to inhibit human tumor growth from preclinical models were achieved along with concomitant pharmacodynamic effects. These data, along with a durable PR observed in the highest dose cohort, support further development of RGX-202. Consequently, dose escalation in combination with FOLFIRI in patients with advanced GI cancers is underway with plans for expansion in CKB+ CRC pts. Clinical trial information: NCT03597581 . [Table: see text]

Abstract CT014: Initial results from the Phase I study of MSC-1, a humanized anti-LIF monoclonal antibody, in patients with advanced solid tumors

Background: Leukemia Inhibitory Factor (LIF) is a pleiotropic cytokine involved in many physiological and pathological processes. LIF is highly expressed in a subset of tumors across multiple solid tumor types and has been shown to correlate with poor prognosis. LIF is hypothesized to contribute to tumor growth and progression by acting on multiple aspects of cancer biology, including immunosuppression of the tumor microenvironment (TME), and regulation of cancer initiating cells (CICs), which are thought to underpin tumor growth, metastasis, and resistance to therapy. MSC-1 is a first-in-class humanized IgG1 monoclonal antibody that potently and selectively inhibits LIF. Blocking LIF with MSC-1 decreased tumor growth in multiple mouse tumor models, drove reprogramming of the TME through effects on immunosuppressive macrophages, and generated durable regressions when combined with anti-PD1. These findings form the basis of a robust therapeutic hypothesis, that MSC-1 treatment may lead to clinical activity in multiple cancer indications. Methods: The Phase 1 study of MSC-1 is enrolling patients with advanced relapsed/refractory solid tumors. The study employs an accelerated 3+3 escalation design to explore safety, PK, LIF peripheral target engagement, immuno-regulatory activity, and preliminary anti-tumor activity of MSC-1. Patients receive treatment with MSC-1 intravenously once every three-weeks until confirmed disease progression or intolerable toxicity. At the top three dose levels, the cohorts will be expanded to further assess safety, PK/target engagement, and to preliminarily assess MOA biomarkers in paired pre- and on treatment tumor tissue from patients. The Dose and Expanded Escalation will enroll patients without regard to their pretreatment LIF tumor levels. Results: As of January 28, 2019, dosing has occurred in 14 patients in the 5 preplanned Dose Escalation cohorts (225mg-1500mg) as well as in 15 patients in the expanded cohorts at 750mg and 1125mg doses for additional safety, PK/PD and biomarker analysis, including analysis of pretreatment and on treatment tumor biopsies in a subset. There have been no DLTs observed at any dose, and analysis of data to select a RP2D for Dose Expansion is ongoing.

Citation Format: Alison Schram, Anna Spreafico, Marc Oliva, Irene Brana, Elena Garralda, Nehal Lakhani, Daniel Von Hoff, Erkut Borazanci, Naimish Pandya, Kimberly Hoffman, Robin Hallett, Patricia Giblin, Judit Anido, Adrianne Kelly, Robert Wasserman, Joan Seoane, Lillian Siu, David M. Hyman, Josep Tabernero. Initial results from the Phase I study of MSC-1, a humanized anti-LIF monoclonal antibody, in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT014.

Abstract 1751: MSC-1 is a first-in-class humanized monoclonal antibody that modulates the tumor microenvironment by inhibiting a novel cancer immunotherapy target, LIF

Leukemia Inhibitory Factor (LIF) is a member of the IL-6 family of cytokines and is involved in many physiological and pathological processes including the promotion of an immunosuppressive environment to support embryo implantation, down-regulation of autoimmune processes and the regulation of stem cell homeostasis and differentiation. In cancer, LIF is hypothesized to have a complex role tumor development and progression, creating an immunosuppressive tumor microenvironment as well as promoting the activity of cancer initiating cells (CICs). LIF is highly expressed in a subset of tumors across multiple tumor types, e.g. glioblastoma multiforme (GBM), non-small cell lung cancer (NSCLC), colon, ovarian, prostate, and pancreatic cancer, and correlates with poor prognosis. Given the pleiotropic role LIF is hypothesized to play in cancer, inhibition of LIF represents an exciting new therapeutic concept sitting at the intersection of two key therapeutic approaches in oncology: blockade of tumor evasion of the immune system and blockade of tumor growth via inhibition of CICs. We have identified and developed MSC-1, a first-in-class humanized IgG1 monoclonal antibody that is a potent and selective inhibitor of LIF. MSC-1 cross reacts with mouse and non-human primate LIF and inhibits LIF signaling by blocking the recruitment of gp130 to the LIF-LIFR-gp130 signaling complex. The efficacy of MSC-1 was evaluated in multiple mouse tumor models and the mechanism of action investigated. LIF inhibition with MSC-1 or shRNAs reduced tumor growth in multiple syngeneic tumor models (NSCLC, ovarian and colon), and clear target engagement was shown for MSC-1. Investigations into the mechanism of action identified that inhibition of LIF with MSC-1 reprogrammed the tumor microenvironment by decreasing immunosuppressive M2 macrophages and increasing the number of intratumoral NK cells and total/activated T cells. MSC-1 also decreased immunosuppressive M2 macrophages in an orthotopic GBM xenograft model and human GBM organotypic tumor slices in an ex vivo model. Similarly, immunosuppressive macrophage genes were decreased when monocytes were co-cultured with supernatants from a GBM cell line in which LIF expression had been knocked-down. Given the effects of MSC-1 on intratumoral immune cells, we hypothesized that MSC-1 could be effectively combined with checkpoint inhibitors and we are currently evaluating MSC-1/checkpoint inhibitor combination therapy. Taken together, these findings form the basis of a robust therapeutic hypothesis, whereby MSC-1 treatment will lead to clinical activity in multiple cancer indications. A Phase I dose-escalation and expansion study of MSC-1 is planned to initiate early 2018 in patients with advanced solid tumors that will incorporate target engagement and PD biomarkers, as well as safety and efficacy endpoints.

Citation Format: Angus Sinclair, Robin Hallett, Patricia Giblin, Isabel Huber-Ruano, Judit Anido, Naimish Pandya, Kimberly Hoffman, Ada Sala, Monica Pascual, Vanessa Chigancas, Swetha Raman, Johan Fransson, Jean-Philippe Julien, Robert Wasserman, Jeanne Magram, Joan Seoane. MSC-1 is a first-in-class humanized monoclonal antibody that modulates the tumor microenvironment by inhibiting a novel cancer immunotherapy target, LIF [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1751.

Abstract LB-B34: LIF as a novel cancer immunotherapy target: modulating the tumor microenvironment with MSC-1, a humanized anti-LIF monoclonal antibody

Leukemia Inhibitory Factor (LIF) is a pleiotropic cytokine involved in many physiological and pathological processes. LIF is highly expressed in a subset of tumors across multiple tumor types and has been shown to correlate with poor prognosis. LIF is hypothesized to contribute to tumor growth and progression by acting on multiple aspects of cancer biology, including immunosuppression of the tumor microenvironment and is a key regulator of cancer initiating cells (CICs). MSC-1, a first-in-class, humanized monoclonal antibody (IgG1), is a potent and selective inhibitor of LIF. MSC-1 leads to STAT3 inhibition by disrupting LIF signaling through the LIF receptor (LIFR). Blocking LIF with MSC-1 decreased tumor growth in multiple mouse tumor models and drove reprogramming of the tumor microenvironment through modulation of immunosuppressive macrophages and of several immune cell types. These findings form the basis of a robust therapeutic hypothesis, whereby MSC-1 treatment may lead to clinical activity in multiple cancer indications. Clinical testing is planned to initiate in the end of 2017 and trials will incorporate target engagement and PD biomarkers as well as efficacy endpoints.

Citation Format: Jeanne Magram, Naimish Pandya, Kimberly Hoffman, Robin Hallett, Patricia Giblin, Angus Sinclair, Judit Anido, Isabel Huber Ruano, Ada Sala, Monica Pascual, Vanessa Chiganças, Robert Wasserman, Joan Seoane. LIF as a novel cancer immunotherapy target: modulating the tumor microenvironment with MSC-1, a humanized anti-LIF monoclonal antibody [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr LB-B34.

Measurement of atmospheric neutrino oscillations with IceCube

We present the first statistically significant detection of neutrino oscillations in the high-energy regime (>20 GeV) from an analysis of IceCube Neutrino Observatory data collected in 2010 and 2011. This measurement is made possible by the low-energy threshold of the DeepCore detector (~20 GeV) and benefits from the use of the IceCube detector as a veto against cosmic-ray-induced muon background. The oscillation signal was detected within a low-energy muon neutrino sample (20-100 GeV) extracted from data collected by DeepCore. A high-energy muon neutrino sample (100 GeV-10 TeV) was extracted from IceCube data to constrain systematic uncertainties. The disappearance of low-energy upward-going muon neutrinos was observed, and the nonoscillation hypothesis is rejected with more than 5σ significance. In a two-neutrino flavor formalism, our data are best described by the atmospheric neutrino oscillation parameters |Δm(32)(2)|=(2.3(-0.5)(+0.6))×10(-3) eV(2) and sin(2)(2θ(23))>0.93, and maximum mixing is favored.

First observation of PeV-energy neutrinos with IceCube

We report on the observation of two neutrino-induced events which have an estimated deposited energy in the IceCube detector of 1.04±0.16 and 1.14±0.17 PeV, respectively, the highest neutrino energies observed so far. These events are consistent with fully contained particle showers induced by neutral-current ν(e,μ,τ) (ν(e,μ,τ)) or charged-current ν(e) (ν(e)) interactions within the IceCube detector. The events were discovered in a search for ultrahigh energy neutrinos using data corresponding to 615.9 days effective live time. The expected number of atmospheric background is 0.082±0.004(stat)(-0.057)(+0.041)(syst). The probability of observing two or more candidate events under the atmospheric background-only hypothesis is 2.9×10(-3) (2.8σ) taking into account the uncertainty on the expected number of background events. These two events could be a first indication of an astrophysical neutrino flux; the moderate significance, however, does not permit a definitive conclusion at this time.

Measurement of the atmospheric νe flux in IceCube

We report the first measurement of the atmospheric electron neutrino flux in the energy range between approximately 80 GeV and 6 TeV, using data recorded during the first year of operation of IceCube's DeepCore low-energy extension. Techniques to identify neutrinos interacting within the DeepCore volume and veto muons originating outside the detector are demonstrated. A sample of 1029 events is observed in 281 days of data, of which 496±66(stat)±88(syst) are estimated to be cascade events, including both electron neutrino and neutral current events. The rest of the sample includes residual backgrounds due to atmospheric muons and charged current interactions of atmospheric muon neutrinos. The flux of the atmospheric electron neutrinos is consistent with models of atmospheric neutrinos in this energy range. This constitutes the first observation of electron neutrinos and neutral current interactions in a very large volume neutrino telescope optimized for the TeV energy range.

Search for dark matter annihilations in the sun with the 79-string IceCube detector

We have performed a search for muon neutrinos from dark matter annihilation in the center of the Sun with the 79-string configuration of the IceCube neutrino telescope. For the first time, the DeepCore subarray is included in the analysis, lowering the energy threshold and extending the search to the austral summer. The 317 days of data collected between June 2010 and May 2011 are consistent with the expected background from atmospheric muons and neutrinos. Upper limits are set on the dark matter annihilation rate, with conversions to limits on spin-dependent and spin-independent scattering cross sections of weakly interacting massive particles (WIMPs) on protons, for WIMP masses in the range 20-5000  GeV/c2. These are the most stringent spin-dependent WIMP-proton cross section limits to date above 35  GeV/c2 for most WIMP models.

Study design and baseline description of the BMI2 trial: reducing paediatric obesity in primary care practices

OBJECTIVES

This study will test the efficacy of motivational interviewing (MI) conducted by primary care providers and dieticians among children ages 2-8 years old with a body mass index (BMI) ≥ 85th and ≤ 97th percentile.

METHODS

Forty-two practices from the American Academy of Pediatrics, Pediatric Research in Office Settings Network were assigned to one of three groups. Group 1 (usual care) measures BMI percentile at baseline, and at 1- and 2-year follow-ups and receives standard health education materials. Group 2 providers deliver three proactive MI counselling sessions with a parent of the index child in Year 1 and one additional 'booster' visit in Year 2. Group 3 adds six MI counselling sessions from a trained dietician. The primary outcome is the child's BMI percentile at 2-year follow-up. Secondary outcomes include parent report of the child's screen time, physical activity, intake of fruits and vegetables, and sugar-sweetened beverages.

RESULTS

We enrolled 633 eligible children whose mean BMI percentile was 92.0 and mean age of 5.1. The cohort was 57% female. Almost 70% of parents reported a household income of ≥ $40,000 per year, and 39% had at least a college education. The cohort was 63% white, 23% Hispanic, 7% black and 7% Asian. Parent self-reported confidence that their child will achieve a healthy weight was on average an 8 (out of 10).

CONCLUSION

To date, several aspects of the study can inform similar efforts including our ability to use volunteer clinicians to recruit participants and their willingness to dedicate their time, without pay, to receive training in MI.

Outbreak of Serratia marcescens infections following injection of betamethasone compounded at a community pharmacy

BACKGROUND

In June 2001, following the report of 4 patients with Serratia marcescens meningitis who received epidural injections of betamethasone compounded at a community pharmacy, we initiated an outbreak investigation.

METHODS

All patients who received injections of betamethasone from the production lot common to the 4 patients were evaluated. A case patient was defined as a patient who received compounded betamethasone and had S. marcescens isolated from a sterile site or clinical and laboratory evidence of infection. We cultured all recovered betamethasone, environmental specimens from the pharmacy, and medications recovered from an ambulatory surgery center. The California Board of Pharmacy reviewed the procedures used to prepare the betamethasone.

RESULTS

We identified 11 patients with culture-confirmed S. marcescens (8 patients) or clinical infection (3 patients) following injection of compounded betamethasone from 25 May through 31 May 2001. Case patients had meningitis (5 patients, with 3 deaths), epidural abscesses (5 patients), or an infected hip (1 patient). S. marcescens was isolated from 35 (69%) of 51 betamethasone vials recovered, from pharmacy specimens of 1% carboxymethylcellulose stock solution, from pharmacy surfaces, and from multiple parenteral materials used at the ambulatory surgery center. Pulsed-field gel electrophoresis patterns of S. marcescens isolates of representative specimens from patients, the betamethasone, the pharmacy, and the ambulatory surgery center were identical. Deficient practices in compounding of betamethasone included inadequate autoclaving temperatures and failure to perform terminal sterilization.

CONCLUSIONS

This outbreak of serious S. marcescens infection followed improper compounding of betamethasone in a community pharmacy. Enforceable national standards for pharmaceutical compounding are needed to reduce the risk of such outbreaks.

Identification of biomarkers for tumor endothelial cell proliferation through gene expression profiling

Extensive efforts are under way to identify antiangiogenic therapies for the treatment of human cancers. Many proposed therapeutics target vascular endothelial growth factor (VEGF) or the kinase insert domain receptor (KDR/VEGF receptor-2/FLK-1), the mitogenic VEGF receptor tyrosine kinase expressed by endothelial cells. Inhibition of KDR catalytic activity blocks tumor neoangiogenesis, reduces vascular permeability, and, in animal models, inhibits tumor growth and metastasis. Using a gene expression profiling strategy in rat tumor models, we identified a set of six genes that are selectively overexpressed in tumor endothelial cells relative to tumor cells and whose pattern of expression correlates with the rate of tumor endothelial cell proliferation. In addition to being potential targets for antiangiogenesis tumor therapy, the expression patterns of these genes or their protein products may aid the development of pharmacodynamic assays for small molecule inhibitors of the KDR kinase in human tumors.

Changes in haemoglobin during interferon alpha-2b plus ribavirin combination therapy for chronic hepatitis C virus infection

Interferon alpha and ribavirin (RBV) combination therapy is associated with decreases in haemoglobin (Hb) concentrations and anaemia. The aim of this analysis was to better characterize the magnitude and frequency of Hb changes and risk factors. This retrospective analysis evaluated treatment-related changes in Hb in 677 patients who participated in either of two interferon alpha-2b plus RBV studies for chronic hepatitis C virus (HCV) infection. Study 1 included 192 interferon alpha-naïve patients randomized to receive RBV 1000-1200 mg/day plus interferon alpha-2b 3 million IU daily or three times weekly for 48 weeks. Study 2 included 485 interferon alpha-experienced patients randomized to receive RBV 1000-1200 mg daily plus interferon alpha-2b 3 million IU daily or three times weekly for 4 weeks, followed by three times weekly dosing for 44 weeks. More than 50% of all patients experienced a decrease in Hb > or =30 g/L. Women were 4.4 times as likely as men to experience a Hb level of <100 g/L; however, men were at a 40% higher risk to experience a Hb decline of >30 g/L from baseline. Daily use of interferon alpha-2b did not impact the magnitude of Hb decrease. In this pooled analysis, RBV dose reduction resulted in increases in Hb concentration of approximately 10 g/L. Lower baseline creatinine clearance, higher baseline Hb levels and increased age were independently associated with increased risk of Hb decreases of >27.7%. Lower baseline weight was not associated with increased risk of Hb decrease. Substantial Hb decreases occur frequently with interferon alpha/RBV combination therapy. Sex, the magnitude of the Hb decline and renal function are potentially important factors to consider in patients receiving RBV. Further research is needed to determine the impact on virological response and to develop strategies to manage the medical consequences.

Rapamycin is active against B-precursor leukemia in vitro and in vivo, an effect that is modulated by IL-7-mediated signaling

A balance between survival and apoptotic signals regulates B cell development. These signals are tightly regulated by a host of molecules, including IL-7. Abnormal signaling events may lead to neoplastic transformation of progenitor B cells. Signal transduction inhibitors potentially may modulate these abnormal signals. Inhibitors of the mammalian target of rapamycin (mTOR) such as rapamycin have been used as immunosuppressive agents. We hypothesized that rapamycin might demonstrate activity against B-precursor acute lymphoblastic leukemia. We have found that rapamycin inhibited growth of B-precursor acute lymphoblastic leukemia lines in vitro, with evidence of apoptotic cell death. This growth inhibition was reversible by IL-7. One candidate as a signaling intermediate cross-regulated by rapamycin and IL-7 was p70 S6 kinase. Rapamycin also demonstrated in vivo activity in E mu-ret transgenic mice, which develop pre-B leukemia/lymphoma: E mu-ret transgenic mice with advanced disease treated daily with rapamycin as a single agent showed a >2-fold increase in length of survival as compared with symptomatic littermates who received vehicle alone. These results suggest that mammalian target of rapamycin inhibitors may be effective agents against leukemia and that one of the growth signals inhibited by this class of drugs in precursor B leukemic cells may be IL-7-mediated.

Cytoplasmic micro heavy chain confers sensitivity to dexamethasone-induced apoptosis in early B-lineage acute lymphoblastic leukemia

Most childhood acute lymphoblastic leukemia (ALL) arises from early B-lineage cells,and response to steroid treatment is critical to successful ALL therapy. To investigate the effect of the pre-B cell receptor (pre-BCR) complex on the response of leukemic cells to steroids, cytoplasmic micro protein (cyto mu) was transfected into cyto mu-, steroid-resistant early B cell lines. The presence of cyto mu and the assembled pre-BCR complex conferred sensitivity to dexamethasone-induced apoptosis. Both intrinsic and extrinsic apoptosis pathways are involved in this cell death. However, if the transfected cyto micro protein is unable to assemble the pre-BCR complex, the cells remain resistant to dexamethasone. These findings suggest a role for the pre-BCR complex in the response of ALL cells to treatment and provide insight into the mechanism of steroid response in the treatment of pre-B ALL.

Response by B cell precursors to pre-B receptor assembly: differences between fetal liver and bone marrow

The expression of different sets of immunoglobulin specificities by fetal and adult B lymphocytes is a longstanding puzzle in immunology. In the past few years it has become clear that production of mu heavy chain and subsequent assembly with surrogate light chain to form the pre-B cell receptor complex is critical to promote development of adult B cell precursors in mouse bone marrow. Recently we found that instead of promoting pre-B cell expansion as in adult bone marrow, this complex inhibits pre-B cell growth in fetal liver, providing a previously unrecognized mechanism for alteration of the B cell repertoire with age. The consequence is very distinct primary repertoires for development of fetal B1 cells and adult bone marrow B2 cells.

Primary care treatment of pediatric psychosocial problems: A study from pediatric research in office settings and ambulatory sentinel practice network

OBJECTIVE

Psychosocial problems cause much of the morbidity among children, and their frequency of presentation in primary care is growing. How is primary care treatment of children's psychosocial problems affected by child symptoms, physician training, practice structure, insurance, physician/patient relationship, and family demographics?

DESIGN

Questionnaire study of treatment of psychosocial problems during office visits by children.

SETTINGS

At total of 401 primary care offices from 44 US states, Puerto Rico, and Canada.

PATIENTS

From 21 150 children seen in office visits, we selected children with an identified psychosocial problem but who were not already receiving specialty mental health services (n = 2618 children).

OUTCOME MEASURES

Clinicians' decisions to counsel families, to refer children to mental health specialists, or to prescribe medication.

RESULTS

The treatment choices of primary care clinicians (PCCs) were generally independent of patients' demographics or insurance status. Clinicians' training, beliefs about mental health, and practice structure had no effect on treatment choices. However, clinicians seeing their own patients were more likely to prescribe medications for attention problems. The clinician's perception about whether the parent agreed with the treatment choice was important for every treatment modality. Counseling and referral were more common and medication was less common when a problem was newly recognized at the visit.

CONCLUSIONS

Structural factors such as practice type, insurance coverage, and physician training were less important for treatment than were process factors, such as whether the visit was a psychosocial problem visit, whether the problem was newly or previously recognized, and whether the family and clinician were familiar with each other and in accord about treatment.

Stable enterovirus 5' nontranslated region over a 7-year period in a patient with agammaglobulinemia and chronic infection

Cerebrospinal fluid samples obtained 7 years apart from a patient with chronic meningoencephalitis and underlying agammaglobulinemia were examined to determine enteroviral genotypic variability. From each sample, amplicons spanning 496 nucleotides within the 5' nontranslated region were generated directly from the cerebrospinal fluid and analyzed. A consensus sequence derived from 3 clones of each amplicon revealed only 7 nucleotide changes over the 7-year period within the region studied. The observed 5' nontranslated region mutation rate in this patient ( approximately 0.2% per year) was significantly lower than mutation rates reported for the poliovirus genome.

Peer group training of pragmatic skills in adolescents with acquired brain injury

OBJECTIVE

To empirically evaluate a method of treating adolescents with cognitive communication disorders, including pragmatic deficits, secondary to acquired brain injury (ABI) in a group setting by objectively measuring outcomes before treatment and immediately after treatment and at 6 months posttreatment.

DESIGN

A before-after trial with follow-up in a consecutive sample, with no control group.

SETTING

Inpatient and outpatient pediatric rehabilitation center.

SUBJECTS

Adolescents who demonstrated pragmatic deficits and scored a rating of 3 or less on each subdomain of the Rehabilitation Institute of Chicago Rating Scale of Pragmatic Communication Skills (RICE-RSPCS) were eligible for the study. Eight subjects were recruited into the study, and two subjects were lost to follow-up. Thus, six of the eight completed the study.

MAIN OUTCOME MEASURES

RICE-RSPCS, Communication Performance Scale (CPS).

RESULTS

Clinically relevant and statistically significant (P <.01) changes occurred during the treatment and were maintained at follow-up for the four RICE-RSPCS subscales and the CPS.

CONCLUSION

These results suggest that the potential and often typical long-term pragmatic and subsequent social difficulties associated with ABI can possibly be lessened through effective intervention.

The fetal origin of B-precursor leukemia in the E-mu-ret mouse

Before the clinical onset of B-precursor lymphoblastic leukemia, E-mu-ret mice have an expansion of late pro-B cells (CD45R+CD43(+)CD24(+)BP-1(+)) within the bone marrow. To characterize the early effects of the transgene product on lymphopoiesis, we initially sequenced the Ig heavy chain (IgH) rearrangements within the late pro-B cells in 24-day-old E-mu-ret and transgene negative mice. In both mouse populations, the IgH rearrangements were polyclonal, predominately nonproductive, and exhibited similar V, D, and J gene usage. However, the frequency of N regions, a marker of postnatal lymphopoiesis, was notably different. At the VD junction, N regions were found in 25 of 25 (100. 0%) rearrangements from transgene-negative mice compared with 12 of 36 (33.3%) rearrangements from Emicro-ret mice. At the DJ junction, N regions were found in 21 of 25 (84.0%) rearrangements from transgene negative mice compared with 4 of 36 (11.1%) rearrangements from E-mu-ret mice. Subsequently, we sequenced the clonal IgH rearrangements from 9 leukemias that developed in 10-to 38-week-old mice and found that 7 leukemias had a least 1 rearrangement that lacked N regions at the DJ junction. In addition, V replacement events were observed in the 1 leukemia studied in detail. Terminal deoxynucleotidyl transferase, the enzyme responsible for N region addition, was expressed at markedly lower levels in late pro-B cells from 7- to 10-day-old E-mu-ret mice compared with transgene-negative mice. Examination of fetal lymphopoiesis in E-mu-ret mice identified a relative increase in early (CD45R+CD43(+)CD24(+)BP-1(-)) and late pro-B cells and a decrease in more differentiated CD43(-) B-lineage cells. Fetal early pro-B cells from Emicro-ret mice proliferated threefold to fivefold greater but differentiated to a lesser extent than those from transgene negative mice when cultured in vitro with interleukin-7. These data suggest that the B precursor leukemias in adult E-mu-ret mice arise from the progeny of pro-B cells generated in utero.

The evolution of B precursor leukemia in the Emu-ret mouse

Emu-ret mice carrying an RFP/RET fusion gene under the transcriptional control of the immunoglobulin heavy chain enhancer develop B lineage leukemias/lymphomas. We have characterized B-cell development in these mice before the onset of clinical disease to determine the steps involved in leukemogenesis. Flow cytometry reveals that the CD45R+CD43(+)CD24(+)BP-1(+) late pro-B-cell population is markedly expanded in the bone marrow of 3- to 5-week-old Emu-ret mice. Compared with late pro-B cells from transgene-negative mice, Emu-ret late pro-B cells have a limited capacity to differentiate in interleukin (IL)-7 and a higher incidence of VDJ rearrangements, but a similar cell cycle profile. In contrast, CD45R+CD43(+)CD24(+)BP-1(-) early pro-B cells from 3- to 5-week-old Emu-ret mice, which also express the RFP/RET transgene, differentiate in IL-7 similarly to their normal counterparts. Furthermore, early pro-B cells from Emu-ret and transgene-negative mice have an identical pattern of growth inhibition when exposed to interferons (IFNs)-alpha/beta and -gamma, whereas, pro-B-cell leukemia lines derived from Emu-ret mice are markedly less sensitive to growth inhibition by these IFNs. In 13-week-old well-appearing Emu-ret mice, late pro-B cells upregulate CYCLIN D1 expression and downregulate CASPASE-1 expression in a pattern that correlates with the emergence of B precursor cells in the peripheral blood and the loss of other B lineage subsets in the bone marrow. Taken together, these results suggest that the expression of the RFP/RET transgene initially prevents the normal elimination of late pro-B cells with nonproductive rearrangements. Secondary events that simultaneously disturb the normal transcriptional regulation of genes involved in the control of the cell cycle and apoptosis may allow for subsequent malignant transformation within the expanded late pro-B-cell population.

A novel mechanism for B cell repertoire maturation based on response by B cell precursors to pre-B receptor assembly

The expression of different sets of immunoglobulin specificities by fetal and adult B lymphocytes is a long-standing puzzle in immunology. Recently it has become clear that production of immunoglobulin mu heavy chain and subsequent assembly with a surrogate light chain to form the pre-B cell receptor complex is critical for development of B cells. Here we show that instead of promoting pre-B cell progression as in adult bone marrow, this complex inhibits pre-B cell growth in fetal liver. Curiously, we identify a fetal-associated VH11 mu heavy chain that allows continued pre-B proliferation in fetal liver. Interestingly, this heavy chain does not associate efficiently with a surrogate light chain, providing a previously unrecognized mechanism for skewing the expression of distinctive VH genes toward fetal through early neonatal life.

The human PD-1 gene: complete cDNA, genomic organization, and developmentally regulated expression in B cell progenitors

We report the complete cDNA sequence and the genomic structure of the human PD-1 homologue. An analysis of the expression pattern of the human PD-1 gene (hPD-1) and the murine PD-1 gene (mPD-1) in developing bone marrow B-lineage cells was also undertaken. The full length hPD-1 cDNA is 2106 nucleotides long and encodes a predicted protein of 288 amino acid residues. The hPD-1 and mPD-1 genes share 70% homology at the nucleotide level and 60% homology at the amino acid level. Four potential sites for N-linked glycosylation are conserved, as are a stretch of amino acids between two cysteine residues resembling a V-set immunoglobulin domain, and another region containing a motif similar to an immunoreceptor tyrosine-based inhibitory motif. Isolation of the genomic locus of the hPD-1 gene reveals that the gene is composed of five exons located on human chromosome 2 at band q37. The 5' flanking region lacks TATA and CAAT cis-acting elements, but includes a number of potential transcription factor binding sites and a dominant transcription start site. The mPD-1 gene was preferentially expressed in pro-B cells from murine adult bone marrow. Although hPD-1 was not preferentially expressed in pro-B cells from human fetal bone marrow, treatment of isolated pro-B cells with interleukin-7 resulted in a dramatic increase in expression. These data suggest that PD-1 may play a role in B-cell differentiation during the pro-B cell stage.

Down-regulation of terminal deoxynucleotidyl transferase by Ig heavy chain in B lineage cells

The enzyme terminal deoxynucleotidyl transferase (TdT) adds nontemplate-derived nucleotides (N regions) to the junctions between recombining variable, diversity, and joining segments of Ig genes. The relative paucity of N regions in Ig light chains, together with the down-regulation of TdT transcription in pre-B cells (prior to light chain production), suggested that production of IgM heavy chain (mu) protein might negatively regulate TdT expression. In this study, we examined the effect of mu production on TdT gene expression in B lineage subsets from normal mice, from recombination-deficient mice (SCID and Rag-1-) carrying mu transgenes, and in transformed pro-B cell lines transfected with mu constructs. In normal mice, TdT is sharply down-regulated at the early pre-B stage in which cells have just completed productive mu rearrangement. Furthermore, the expression of mu transgenes in pro-B stage cells from recombination-deficient mice results in a similar decrease. Finally, transfection of genomic constructs encoding mu into pro-B cell lines results in a marked reduction of TdT expression. Taken together, these findings indicate that mu protein production results in the down-regulation of TdT. The ability of mu transgenes to alter TdT expression in cell lines also suggests that signaling through the pre-B receptor does not necessarily require interaction with an external stromal cell-derived ligand.

The influence of provider behavior, parental characteristics, and a public policy initiative on the immunization status of children followed by private pediatricians: a study from Pediatric Research in Office Settings

OBJECTIVES

To determine the relative impact of parental characteristics, provider behavior, and the provision of free vaccines through state-sponsored vaccine volume programs (VVPs) on the immunization status of children followed by private pediatricians.

STUDY DESIGN

Retrospective and cross-sectional surveys of immunization data.

SETTING

The offices of 15 private pediatricians, from 11 states, who were members of the Pediatric Research in Office Settings network. Seven of these physicians used vaccines provided through VVPs.

PATIENTS

Children 2 to 3 years old followed by the participating physicians.

METHODS

The immunization status of children was assessed from two separate samples. For sample 1, immunization data were abstracted from the medical records of 60 consecutive eligible children seen in each office. Parents of the selected children indicated the method of payment for immunizations and the education levels of the mothers. Because this cross-sectional survey might have oversampled frequent health care users, a retrospective chart review of up to 75 randomly selected children in each pediatrician's practice was also conducted (sample 2). Additional data were collected from the parents of children in sample 2 by telephone interviews. For both samples, patients were considered to be fully immunized if they had received four diphtheria-tetanus-pertussis/diphtheria-tetanus vaccines, three oral poliovirus/inactivated poliovirus vaccines, and one measles-mumps-rubella vaccine before their second birthdays. Before collecting vaccination data, pediatricians completed a survey detailing their immunization beliefs and practices. Logistic regression was used to identify factors that were independently associated with a child being fully immunized.

RESULTS

For sample 1, 81.7% of the 857 children surveyed were fully immunized. Practitioner-specific immunization rates varied widely, ranging from 51% to 97%. The immunization rate of children who received vaccines provided by VVPs was similar to that of children whose immunizations were not provided by VVPs (81.2% vs 82.2%; odds ratio [OR] for a VVP as a predictor for being fully immunized, 0.94, 95% confidence interval [CI], 0.66 to 1.32). In addition, parents who paid for immunizations out of pocket were as likely to have fully immunized children as those who had little or no out-of-pocket expenditures for vaccines (OR, 1.13; 95% CI, 0.75 to 1.13). In the logistic model, only individual pediatrician and size of the metropolitan area in which the pediatrician's practice was located were significant predictors of a child's immunization status. The results from sample 2 were similar; 82.1% of the 772 surveyed patients were fully immunized. With sample 2, individual pediatrician and age of the child at the time of the survey were the only predictors of immunization status. The OR of a VVP as a predictor of a child being fully immunized was 1.37 (95% CI, 0.65 to 2.90).

CONCLUSIONS

Individual provider behavior may be the most important determinant of the immunization status of children followed by private pediatricians. In our samples, the effect of parental characteristics was limited. State-sponsored VVPs were not associated with higher immunization rates, perhaps because cost of vaccines did not seem to be a significant barrier to immunization in this population.

Down-regulation of terminal deoxynucleotidyl transferase by Ig heavy chain in B lineage cells

The enzyme terminal deoxynucleotidyl transferase (TdT) adds nontemplate-derived nucleotides (N regions) to the junctions between recombining variable, diversity, and joining segments of Ig genes. The relative paucity of N regions in Ig light chains, together with the down-regulation of TdT transcription in pre-B cells (prior to light chain production), suggested that production of IgM heavy chain (mu) protein might negatively regulate TdT expression. In this study, we examined the effect of mu production on TdT gene expression in B lineage subsets from normal mice, from recombination-deficient mice (SCID and Rag-1-) carrying mu transgenes, and in transformed pro-B cell lines transfected with mu constructs. In normal mice, TdT is sharply down-regulated at the early pre-B stage in which cells have just completed productive mu rearrangement. Furthermore, the expression of mu transgenes in pro-B stage cells from recombination-deficient mice results in a similar decrease. Finally, transfection of genomic constructs encoding mu into pro-B cell lines results in a marked reduction of TdT expression. Taken together, these findings indicate that mu protein production results in the down-regulation of TdT. The ability of mu transgenes to alter TdT expression in cell lines also suggests that signaling through the pre-B receptor does not necessarily require interaction with an external stromal cell-derived ligand.

Identification of the earliest B lineage stage in mouse bone marrow

We have identified a very early stage of B lineage cells in the CD45R (B220)+CD24 (HSA) pre-pro-B fraction of mouse bone marrow delineated by expression of AA4.1, a molecule found on stem cells and early B lineage cells. These cells are B lineage precursors based on their capacity to generate B lineage cells rapidly in stromal-dependent culture and their expression of high levels of germline IgH transcripts in the absence of Rag-1/2. Half of these AA4.1+ precursors express low levels of CD4, characteristic of lymphoid progenitors, but few if any have up-regulated CD19, a molecule expressed very early in the B lineage. Furthermore, expression of genes encoding pre-B and B cell receptor components (mb-1, B29, and lambda 5) and transcription factors necessary for B lineage differentiation (BSAP, E12, E47, and Id) provide further support for designating these cells as the earliest B cell precursors.

A patient-specific in vivo tumor model

A significant body of research, spanning approximately the last 25 years, has focused upon the task of developing a better understanding of tumor growth through the use of in vitro mathematical models. Although such models are useful for simulation, in vivo growth differs in significant ways due to the variety of competing biological, biochemical, and mechanical factors present in a living biological system. An in vivo, macroscopic, primary brain tumor growth model is developed, incorporating previous in vitro growth pattern research as well as scientific investigations into the biological and biochemical factors that affect in vivo neoplastic growth. The tumor growth potential model presents an integrated, universal framework that can be employed to predict the direction and extent of spread of a primary brain tumor with respect to time for a specific patient. This framework may be extended as necessary to include the results of current and future research into parameters affecting neoplastic proliferation. The patient-specific primary brain tumor growth model is expected to have multiple clinical uses, including: predictive modeling, tumor boundary delineation, growth pattern research, improved radiation surgery planning, and expert diagnostic assistance.

Clonal expansion of germline B-lineage acute lymphoblastic leukemia in severe combined immunodeficient mice

CD19+ B lineage acute lymphoblastic leukemias (ALLs) with unrearranged Ig and TCR genes are designated germline B lineage ALLs. We used CDR3 PCR to determine whether pediatric germline B lineage ALLs contain minor subclones with rearranged Ig H V genes. In six of seven cases there were no PCR detectable CDR3 rearrangements. One case with a smear pattern on CDR3 PCR contained multiple unique CDR3 sequences at frequencies of 1-2 per 2,600, suggesting that polyclonal B cells were present at low frequency. To verify that the germline patterns were from leukemic cells and evaluate in vivo subclone differentiation, a germline B lineage ALL with the t(4;11) translocation was propagated in severe combined immunodeficient SCID) mice. The Ig and TCR genes in the leukemic cells recovered from mouse tissues were germline by Southern blot analysis except for single rearrangements that suggested subclone evolution at the Ig H and lambda loci in addition to the germline population. No CDR3 sequences were detected, indicating that the observed Ig H gene rearrangement most likely was a DJ joining. This study suggests that the transformed cell in germline B lineage ALL represents an early pro-B cell with limited tendency to further differentiate.

Differential expression of the blk and ret tyrosine kinases during B lineage development is dependent on Ig rearrangement

Expression of Ig transgenes in recombination-deficient mutant scid and Rag-1-mice results in the generation of pre-B and B cells, which are normally absent from these animals. In screening for protein tyrosine kinases (PTKs) that may play a role in this progression beyond the pro-B stage, we have identified five differentially regulated PTKs and compared their gene expression in defined stages of early B-lineage cells from normal, mutant, and Ig-transgenic mutant mice. Three PTKs (fgr, flk2/flt3, and tsk) show a comparable decrease at an early stage in all mice. In contrast, the decreasing expression of ret and the increasing expression of blk seen in differentiating B cells from normal mice are not observed in the mutant mice, unless they carry Ig transgenes. Therefore, our results show that the expression of certain PTKs is dependent on productive Ig rearrangement and suggest important roles for both Ret and Blk at distinct stages in the Ig-dependent progression of B cell differentiation.

Differential expression of the blk and ret tyrosine kinases during B lineage development is dependent on Ig rearrangement

Expression of Ig transgenes in recombination-deficient mutant scid and Rag-1-mice results in the generation of pre-B and B cells, which are normally absent from these animals. In screening for protein tyrosine kinases (PTKs) that may play a role in this progression beyond the pro-B stage, we have identified five differentially regulated PTKs and compared their gene expression in defined stages of early B-lineage cells from normal, mutant, and Ig-transgenic mutant mice. Three PTKs (fgr, flk2/flt3, and tsk) show a comparable decrease at an early stage in all mice. In contrast, the decreasing expression of ret and the increasing expression of blk seen in differentiating B cells from normal mice are not observed in the mutant mice, unless they carry Ig transgenes. Therefore, our results show that the expression of certain PTKs is dependent on productive Ig rearrangement and suggest important roles for both Ret and Blk at distinct stages in the Ig-dependent progression of B cell differentiation.

Biomedical imaging modalities: a tutorial

The introduction of advanced imaging technologies has improved significantly the quality of medical care available to patients. Non-invasive imaging modalities allow a physician to make increasingly accurate diagnoses and render precise and measured modes of treatment. Current uses of imaging technologies include laboratory medicine, surgery, radiation therapy, nuclear medicine, and diagnostic radiology. This paper provides an overview of most of the popular imaging modalities currently in clinical use. It is hoped that a general understanding of the modality from which an image is derived will help researchers in the subsequent analysis of the image data.

Differentiation stages of childhood acute lymphoblastic leukemias with p53 mutations

Based upon in vitro evidence of p53 involvement in lymphoid differentiation, we assessed immunoglobulin (Ig) and T-cell receptor (TCR) genes in five acute lymphoblastic leukemias (ALLs) with, and 24 ALLs without p53 mutations to compare their genotypic stages. Using Southern blot analysis and complementarity determining region III polymerase chain reaction (CDRIII PCR), 18 cases of B-lineage ALL and 11 cases of T-ALL were studied. Of 20 specimens from 18 B-lineage ALLs, two of four with p53 mutation and two of 16 without mutation had an unrearranged Ig and TCR genotype (p = 0.16; Fisher's exact test). Of 11 cases of T-ALL, the one case with p53 mutation had a rearranged TCR and Ig genotype and a case without mutation was unrearranged. The study indicates that p53 mutation is an infrequent feature of ALL found, nonetheless, in every genotypic subset. The p53 mutations in cases that do not further rearrange may support p53 involvement in lymphoid differentiation, but the heterogeneity in differentiation stages in cases both with and without p53 mutations suggests that regulation of early lymphoid maturation is multifactorial.

Polymorphism at codon 36 of the p53 gene

A polymorphism at codon 36 in exon 4 of the p53 gene was identified by single strand conformation polymorphism (SSCP) analysis and direct sequencing of genomic DNA PCR products. The polymorphic allele, present in the heterozygous state in genomic DNAs of four of 100 individuals (4%), changes the codon 36 CCG to CCA, eliminates a FinI restriction site and creates a BccI site. Including this polymorphism there are four known polymorphisms in the p53 coding sequence.

Identification of an altered immunoglobulin heavy-chain gene rearrangement in the central nervous system in B-precursor acute lymphoblastic leukemia

In B-precursor acute lymphoblastic leukemia (ALL), the nucleotide sequence of the complementarity determining region III (CDRIII) in the rearranged immunoglobulin heavy chain gene (IgH) has been used as a molecular fingerprint to identify the leukemic cells. In a child with B-precursor ALL without central nervous system (CNS) disease at diagnosis and a subsequent isolated CNS relapse, we examined the stability of the rearranged IgH by comparing the nucleotide sequences of the CDRIII in the leukemic cells from the marrow at diagnosis to the sequences in the leukemic cells from the cerebrospinal fluid at relapse. Whereas two of the three IgH sequences isolated from the leukemic cells at CNS relapse were identical to sequences originally isolated from the marrow lymphoblasts at diagnosis, the third CNS sequence was similar but not identical to the third marrow sequence. The third IgH sequence identified in the CNS differed from the marrow sequence only at the variable gene segment adjoining the CDRIII. Using a detection method based on the polymerase chain reaction, the altered IgH sequence identified in the leukemic cells from the cerebrospinal fluid was noted to be present in the CNS at a higher frequency than the related diagnostic sequence and was not detected in the marrow either at diagnosis or at CNS relapse. These findings indicate that the clonal pattern of leukemia in the CNS may differ from that in the marrow.

Molecular residual disease status at the end of chemotherapy fails to predict subsequent relapse in children with B-lineage acute lymphoblastic leukemia

PURPOSE

We have investigated whether the extent of residual leukemia in the marrows obtained at the completion of chemotherapy can predict subsequent relapse in children with B-lineage acute lymphoblastic leukemia (ALL).

PATIENTS AND METHODS

Marrow samples of 24 patients were examined for residual disease at the end of treatment using a quantitative method based on the polymerase chain reaction (PCR) amplification of the complementarity determining region-3 of the immunoglobulin heavy chain.

RESULTS

Of the 15 patients who remain in continuous bone marrow remission (range, 41 to 98 months), 14 had no detectable leukemic cells; one patient had a very low level (one in approximately 335,000 marrow cells) of residual leukemic cells that underwent clonal evolution. Among the nine patients who had a marrow relapse after the completion of treatment, eight patients whose relapses occurred 4 to 54 months from the end of therapy had no detectable leukemic cells, whereas only the one patient who relapsed 2 months after the completion of therapy had detectable residual disease.

CONCLUSION

These observations indicate that the absence of detectable residual leukemia by PCR at the end of chemotherapy is not sufficient to assure that the patient is cured and suggest that frequent serial monitoring is required for the early prediction of relapse off therapy.