Phase 1/2 study of intratumoral G100 (TLR4 agonist) with or without pembrolizumab in follicular lymphoma

Intratumoral injection of G100, a toll-like receptor 4 (TLR4) agonist, was shown pre-clinically to stimulate anti-tumor immune responses and tumor regression. This open-label, multicenter, phase 1/2 trial evaluated the safety, tolerability, and preliminary efficacy of intratumoral G100 injections following localized low-dose radiation in patients with follicular lymphoma (ClinicalTrials.gov #NCT02501473). The study was comprised of a G100 dose escalation (5 or 10 µg/dose, or 20 µg/dose for large tumors); a randomized component comparing G100 to G100 plus pembrolizumab; and G100 20 µg/dose expansion. Adverse events grade ≥3 were uncommon in patients treated with G100, and no unexpected toxicities were observed when combined with pembrolizumab. G100 20 µg (n = 18) resulted in an overall response rate of 33.3% and abscopal tumor regression in 72.2% of patients. This early-phase study provides a foundation for combining an intratumoral TLR4 agonist with agents to produce immune-mediated responses in follicular lymphoma with limited added toxicity.

Phase II Randomized Study of CMB305 and Atezolizumab Compared With Atezolizumab Alone in Soft-Tissue Sarcomas Expressing NY-ESO-1

PURPOSE

CMB305 is a heterologous prime-boost vaccination regimen created to prime NY-ESO-1-specific CD8 T-cell populations and then activate the immune response with a potent TLR-4 agonist. This open-label randomized phase II trial was designed to investigate the efficacy and safety of adding the CMB305 regimen to atezolizumab (anti-programmed death ligand-1 therapy) in comparison with atezolizumab alone in patients with synovial sarcoma or myxoid liposarcoma.

PATIENTS AND METHODS

Patients with locally advanced, relapsed, or metastatic synovial sarcoma or myxoid liposarcoma (any grade) were randomly assigned to receive CMB305 with atezolizumab (experimental arm) or atezolizumab alone (control arm). The primary end points were progression-free survival (PFS) and overall survival (OS) analyzed using the Kaplan-Meier method. Safety and immune responses were assessed.

RESULTS

A total of 89 patients were enrolled; 55.1% had received ≥ 2 prior lines of chemotherapy. Median PFS was 2.6 months and 1.6 months in the combination and control arms, respectively (hazard ratio, 0.9; 95% CI, 0.6 to 1.3). Median OS was 18 months in both treatment arms. Patients treated with combination therapy had a significantly higher rate of treatment-induced NY-ESO-1-specific T cells (P = .01) and NY-ESO-1-specific antibody responses (P < .0001). In a post hoc analysis of all dosed patients, OS was longer (36 months) in the subset who developed anti-NY-ESO-1 T-cell immune response (hazard ratio, 0.3; P = .02).

CONCLUSION

Although the combination of CMB305 and atezolizumab did not result in significant increases in PFS or OS compared with atezolizumab alone, some patients demonstrated evidence of an anti-NY-ESO-1 immune response and appeared to fare better by imaging than those without such an immune response. Combining prime-boost vaccines such as CMB305 with anti-programmed death ligand-1 therapies merits further evaluation in other clinical contexts.

Clinical outcomes of patients with advanced synovial sarcoma or myxoid/round cell liposarcoma treated at major cancer centers in the United States

BACKGROUND

Outcomes data regarding advanced synovial sarcoma (SS) and myxoid/round cell liposarcoma (MRCL) are limited, consisting primarily of retrospective series and post hoc analyses of clinical trials.

METHODS

In this multi-center retrospective study, data were abstracted from the medical records of 350 patients from nine sarcoma centers throughout the United States and combined into a registry. Patients with advanced/unresectable or metastatic SS (n = 249) or MRCL (n = 101) who received first-line systemic anticancer therapy and had records of tumor imaging were included. Overall survival (OS), time to next treatment, time to distant metastasis, and progression-free survival (PFS) were evaluated using the Kaplan-Meier method and Cox regression.

RESULTS

At start of first-line systemic anticancer therapy, 92.4% of patients with SS and 91.1% of patients with MRCL had metastatic lesions. However, 74.7% of patients with SS and 72.3% of patients with MRCL had ≥2 lines of systemic therapy. Median OS and median PFS from first-line therapy for SS was 24.7 months (95% CI, 20.9-29.4) and 7.5 months, respectively (95% CI, 6.4-8.4). Median OS and median PFS from start of first-line therapy for MRCL was 29.9 months (95% CI, 27-44.6) and 8.9 months (95% CI 4.5-12.0).

CONCLUSIONS

To the best of our knowledge, this is the largest retrospective study of patients with SS and MRCL. It provides an analysis of real-world clinical outcomes among patients treated at major sarcoma cancer centers and could inform treatment decisions and design of clinical trials. In general, the survival outcomes for this selected population appear more favorable than in published literature.

A phase II randomized study of CMB305 and atezolizumab versus atezolizumab in NY-ESO-1+ soft tissue sarcoma: Analysis of immunogenicity, tumor control, and patient survival

11011

Background: CMB305 (C) is an immunotherapy designed to generate an anti-NY-ESO-1 immune response (IR). C consists of a dendritic cell-targeting lentiviral vector encoding NY-ESO-1 gene (LV305), and a TLR-4 agonist NY-ESO-1 recombinant protein plus GLA-SE (G305). A Phase 1 study demonstrated C is safe, generates IR and conveys a median overall survival (mOS) of 23.7 months (15.5, not reached [NR]) for soft tissue sarcomas & 29.2 months (12.2, NR) for synovial sarcoma (SS) (ESMO 2018). We evaluated efficacy and safety of C and atezolizumab (A) vs A alone in NY-ESO-1+ SS and myxoid round cell liposarcoma (MRCL). Methods: A prospective randomized open label phase 2 study of C (LV305 Intradermal Days 0, 14, 42, 70 + G305 Intramuscular Days 28, 56, 84 then q 6wk up to one year (yr)) + A (1200mg IV q3wk) vs A alone in advanced NY-ESO-1+ SS/MRCL. Primary endpoints of OS and progression-free survival (PFS); secondary endpoints of safety, IR, and response rate and post hoc analysis by line of therapy. Results: 88 patients (pts) were enrolled and dosed. Arm C+A: median age 48 yrs, 73% SS, 98% relapsed metastatic, 73% ≥2 prior lines chemotherapy; Arm A: 47 yrs, 67% SS, 84% relapsed metastatic, 53% ≥2 prior lines chemotherapy. Most treatment-related adverse events (TRAE) Grade 1/2, no treatment related deaths. Summary of clinical outcomes. Conclusions: Despite no major differences in PFS and OS between the treatment arms (Arm C+A had more advanced disease and more prior lines of chemotherapy), Arm A +C achieved PRs, a higher level of anti-NY-ESO-1 IR, and pts with IR had numerically superior outcomes. Moreover, the clinical benefit of C+A in earlier lines of therapy warrant further study. Clinical trial information: NCT02609984. [Table: see text]

EGFR Genotyping of Matched Urine, Plasma, and Tumor Tissue in Patients With Non–Small-Cell Lung Cancer Treated With Rociletinib, an EGFR Tyrosine Kinase Inhibitor

Purpose

Liquid biopsies represent an attractive alternative to tissue biopsies, particularly rebiopsies, in determining patient eligibility for targeted therapies. Clinical utility of urine genotyping, however, has not been explored extensively. We evaluated epidermal growth factor receptor ( EGFR) T790M detection in matched urine, plasma, and tissue and the clinical outcomes of patients with advanced non–small-cell lung cancer treated with rociletinib.

Methods

Tissue (n = 540), plasma (n = 482), and urine (n = 213) were collected from evaluable patients enrolled in TIGER-X, a phase I/II study. Genotyping was performed by therascreen EGFR testing in tissue, BEAMing in plasma, and a quantitative short footprint assay (Trovera) in urine, which was used to further examine discordant samples.

Results

Positive percent agreement with tissue T790M results was similar for urine (82%; 142 of 173) and plasma (81%; 313 of 387) genotyping. Urine and plasma together identified more patients who were T790M positive (92%) than tissue alone (83%) among matched samples (n = 177). The ability to identify mutations in plasma was strongly associated with M stage ( P < .001); rate of T790M detection for patients with M1a/M0 disease increased from 54% for plasma alone to 85% when urine and plasma were both examined. Objective response rates of patients who were T790M positive were comparable between tumor (34%), plasma (32%), and urine (37%).

Conclusion

Clinical response to rociletinib was comparable irrespective of whether T790M status was identified by liquid or tissue biopsy. Combined, urine and plasma identified a higher percentage of patients who were T790M positive than tumor genotyping alone and improved detection of T790M, particularly in the absence of distant metastases. These findings support the noninvasive analysis of urine and plasma before tumor rebiopsy when assessing T790M status.

Quality of life results from the phase 3 REVEL randomized clinical trial of ramucirumab-plus-docetaxel versus placebo-plus-docetaxel in advanced/metastatic non-small cell lung cancer patients with progression after platinum-based chemotherapy

OBJECTIVES

REVEL demonstrated that ramucirumab+docetaxel (RAM+DTX) improved overall survival, progression-free survival, and objective response rate in patients with advanced/metastatic non-small cell lung cancer with progression after platinum-based chemotherapy. This analysis examined quality of life (QoL) as assessed by the Lung Cancer Symptom Scale (LCSS) and clinician-reported functional status.

MATERIALS AND METHODS

The LCSS includes 6 symptom and 3 global items measured on a 0-100-mm scale; higher scores represent greater symptom burden. LCSS and ECOG PS data were collected at baseline, every 3-week cycle, the summary visit, and at the 30-day follow-up. LCSS total score and Average Symptom Burden Index (ASBI) were calculated. The primary analysis compared time to deterioration (TtD) between treatment arms for all individual items and summary scores, defined as increase from baseline by ≥ 15 mm using the Kaplan-Meier method and Cox regression. TtD to ECOG PS ≥ 2 was analyzed.

RESULTS

There were 1253 patients randomized to receive RAM+DTX or placebo+docetaxel (PL+DTX). Across all assessments, LCSS compliance was approximately 75% and balanced across arms. The mean (SD) baseline LCSS total score was 27.3mm (17.08 mm) on RAM+DTX and 29.6mm (17.59 mm) on PL+DTX. At 30-day follow-up, mean (SD) LCSS total score was 32.0 (19.03) on RAM+DTX and 32.5 (19.87) on PL+DTX. The TtD for all LCSS scores was similar between treatment arms. Stratified HRs (95% CI) for LCSS total score and ASBI were HR=0.99 (0.81, 1.22), p=0.932 and HR=0.93 (0.75, 1.15), p=0.514 with approximately 70% of patients censored. TtD to PS ≥ 2 was similar between treatment arms (HR=1.03 [95% CI: 0.85, 1.26], p=0.743) with approximately two-thirds of the patients censored.

CONCLUSION

In addition to improvement of clinical efficacy outcomes demonstrated in REVEL, these results suggest that adding ramucirumab to docetaxel did not impair patient QoL, symptoms, or functioning.

Phase 2, randomized, open-label study of ramucirumab in combination with first-line pemetrexed and platinum chemotherapy in patients with nonsquamous, advanced/metastatic non-small cell lung cancer

BACKGROUND

Vascular endothelial growth factor (VEGF)-mediated angiogenesis plays an important role in non-small cell lung cancer (NSCLC). Ramucirumab is a human immunoglobulin G1 monoclonal antibody that inhibits VEGF receptor 2. This phase 2 study investigated ramucirumab in combination with first-line pemetrexed and platinum chemotherapy in advanced/metastatic NSCLC.

METHODS

Eligible stage IV nonsquamous NSCLC patients with no prior chemotherapy for metastatic disease were randomized 1:1 to pemetrexed and carboplatin (or cisplatin) or ramucirumab (10 mg/kg) plus pemetrexed and carboplatin (or cisplatin) once every 3 weeks. Treatment was given for 4 to 6 cycles, and this was followed by a maintenance phase with pemetrexed or ramucirumab and pemetrexed. The primary endpoint was progression-free survival (PFS) with a sample size of sufficient power to detect an increase from 7 to 10.4 months.

RESULTS

From October 2010 to October 2011, 140 patients were randomized (pemetrexed-platinum arm, 71; ramucirumab-pemetrexed-platinum arm, 69), and most baseline characteristics were similar for the 2 treatment arms. The median PFS was 5.6 months for the pemetrexed-platinum arm and 7.2 months for the ramucirumab-pemetrexed-platinum arm (hazard ratio, 0.75; P = .132). The objective response rates were 38.0% and 49.3% for the pemetrexed-platinum and ramucirumab-pemetrexed-platinum arms, respectively (P = .180). The disease control rate was 70.4% for the pemetrexed-platinum arm and 85.5% for the ramucirumab-pemetrexed-platinum arm (P = .032). The grade 3 or higher adverse events occurring in 10% or more of patients were thrombocytopenia, neutropenia, fatigue, anemia, nausea, back pain, and hypertension.

CONCLUSIONS

The primary endpoint of significant prolongation of PFS was not met; however, ramucirumab showed evidence of clinical activity in combination with pemetrexed and platinum in nonsquamous NSCLC patients. The addition of ramucirumab to pemetrexed and platinum did not result in new or unexpected safety findings.

A phase II, open-label study of ramucirumab in combination with paclitaxel and carboplatin as first-line therapy in patients with stage IIIB/IV non-small-cell lung cancer

INTRODUCTION

The objective of this study was to determine whether the addition of ramucirumab to first-line paclitaxel-carboplatin chemotherapy in patients with advanced non-small-cell lung cancer (NSCLC) resulted in a 6-month progression-free survival (PFS) rate that compares favorably with the historic rate for bevacizumab combined with paclitaxel-carboplatin in this patient population.

METHODS

In this phase II, single-arm, open-label, multicenter study, 40 patients with advanced NSCLC received ramucirumab (10 mg/kg intravenous [IV]) followed by paclitaxel (200 mg/m IV) and carboplatin area under the curve = 6 on day 1 every 21 days as first-line therapy. Therapy continued for up to six cycles. Patients not experiencing withdrawal criteria may have continued ramucirumab monotherapy every 3 weeks. The primary endpoint was PFS at 6 months, with 80% power to detect a 6-month PFS rate of at least 55%.

RESULTS

The 6-month PFS rate was 59.0% and the objective response rate was 55.0%. The most common treatment-related adverse events were fatigue, peripheral neuropathy, nausea, epistaxis, and myalgia. Single-nucleotide polymorphism (SNP) rs2981582 on the FGFR-2gene had significant associations with improved overall survival, PFS, and best overall response (p values without multiplicity adjustment were 0.0059, 0.0429, and 0.0392, respectively).

CONCLUSION

Ramucirumab in combination with paclitaxel-carboplatin resulted in a 6-month PFS rate and safety profile that compared favorably with the historical control. In addition, no deaths were associated with this treatment. Furthermore, we describe an association of SNP on FGFR-2 gene with survival and response. These findings warrant further clinical investigation in patients with NSCLC.

Ramucirumab plus docetaxel versus placebo plus docetaxel for second-line treatment of stage IV non-small-cell lung cancer after disease progression on platinum-based therapy (REVEL): a multicentre, double-blind, randomised phase 3 trial

BACKGROUND

Ramucirumab is a human IgG1 monoclonal antibody that targets the extracellular domain of VEGFR-2. We aimed to assess efficacy and safety of treatment with docetaxel plus ramucirumab or placebo as second-line treatment for patients with stage IV non-small-cell-lung cancer (NSCLC) after platinum-based therapy.

METHODS

In this multicentre, double-blind, randomised phase 3 trial (REVEL), we enrolled patients with squamous or non-squamous NSCLC who had progressed during or after a first-line platinum-based chemotherapy regimen. Patients were randomly allocated (1:1) with a centralised, interactive voice-response system (stratified by sex, region, performance status, and previous maintenance therapy [yes vs no]) to receive docetaxel 75 mg/m(2) and either ramucirumab (10 mg/kg) or placebo on day 1 of a 21 day cycle until disease progression, unacceptable toxicity, withdrawal, or death. The primary endpoint was overall survival in all patients allocated to treatment. We assessed adverse events according to treatment received. This study is registered with ClinicalTrials.gov, number NCT01168973.

FINDINGS

Between Dec 3, 2010, and Jan 24, 2013, we screened 1825 patients, of whom 1253 patients were randomly allocated to treatment. Median overall survival was 10·5 months (IQR 5·1-21·2) for 628 patients allocated ramucirumab plus docetaxel and 9·1 months (4·2-18·0) for 625 patients who received placebo plus docetaxel (hazard ratio 0·86, 95% CI 0·75-0·98; p=0·023). Median progression-free survival was 4·5 months (IQR 2·3-8·3) for the ramucirumab group compared with 3·0 months (1·4-6·9) for the control group (0·76, 0·68-0·86; p<0·0001). We noted treatment-emergent adverse events in 613 (98%) of 627 patients in the ramucirumab safety population and 594 (95%) of 618 patients in the control safety population. The most common grade 3 or worse adverse events were neutropenia (306 patients [49%] in the ramucirumab group vs 246 [40%] in the control group), febrile neutropenia (100 [16%] vs 62 [10%]), fatigue (88 [14%] vs 65 [10%]), leucopenia (86 [14%] vs 77 [12%]), and hypertension (35 [6%] vs 13 [2%]). The numbers of deaths from adverse events (31 [5%] vs 35 [6%]) and grade 3 or worse pulmonary haemorrhage (eight [1%] vs eight [1%]) did not differ between groups. Toxicities were manageable with appropriate dose reductions and supportive care.

INTERPRETATION

Ramucirumab plus docetaxel improves survival as second-line treatment of patients with stage IV NSCLC.

FUNDING

Eli Lilly.

REVEL: A randomized, double-blind, phase III study of docetaxel (DOC) and ramucirumab (RAM; IMC-1121B) versus DOC and placebo (PL) in the second-line treatment of stage IV non-small cell lung cancer (NSCLC) following disease progression after one prior platinum-based therapy

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Background: RAM is a human IgG1 monoclonal antibody that targets the extracellular domain of VEGFR-2. The REVEL study evaluated the efficacy and safety of RAM+DOC vs. PL+DOC (DOC) in patients (pts) with stage IV nonsquamous (NSQ) and squamous (SQ) NSCLC after platinum-based therapy. Methods: Pts with NSQ and SQ stage IV NSCLC were randomized 1:1 (stratified by sex, region, ECOG PS, and prior maintenance therapy) to receive DOC 75 mg/m2 in combination with either RAM 10 mg/kg or PL on day 1 of a 21-day cycle until disease progression, unacceptable toxicity, or death. The primary endpoint was overall survival (OS). Secondary efficacy endpoints included progression-free survival (PFS), and objective response rate (ORR). Results: Between Dec 2010 and Feb 2013, 1,253 pts (26.2% SQ) were randomized (RAM+DOC: 628; DOC: 625). Pt characteristics were balanced between arms. ORR was 22.9% for RAM+DOC and 13.6% for DOC (P<0.001). The hazard ratio (HR) for PFS was 0.762 (P<0.0001); median PFS was 4.5 months (m) for RAM+DOC vs. 3.0m for DOC. REVEL met its primary endpoint; the OS HR was 0.857 (95% CI 0.751, 0.98; P=0.0235); median OS was 10.5m for RAM+DOC vs. 9.1m for DOC. OS was longer for RAM+DOC in most pt subgroups, including SQ and NSQ histology. Grade ≥3 adverse events (AEs) occurring in >5% of pts on RAM+DOC were neutropenia (34.9% vs. 28.0%), febrile neutropenia (15.9% vs. 10.0%), fatigue (11.3% vs. 8.1%), leukopenia (8.5% vs. 7.6%), hypertension (5.4% vs. 1.9%), and pneumonia (5.1% vs. 5.8%). Grade 5 AEs were comparable between arms (5.4% vs. 5.8%), as was pulmonary hemorrhage (any grade; all pts: 2.1% vs. 1.6%; SQ pts: 3.8% vs. 2.4%). Conclusions: REVEL demonstrated a statistically significant improvement in ORR, PFS, and OS for RAM+DOC vs DOC in NSCLC pts with stage IV NSCLC as second-line treatment after platinum-based therapy. Benefits were similar in NSQ and SQ pts, and no unexpected AEs were identified. Clinical trial information: NCT01168973.

A randomized, double-blind, phase III study of Docetaxel and Ramucirumab versus Docetaxel and placebo in the treatment of stage IV non-small-cell lung cancer after disease progression after 1 previous platinum-based therapy (REVEL): treatment rationale and study design

This article describes the treatment rationale and study-related procedures for the A Randomized, Double-Blind, Phase 3 Study of Docetaxel and Ramucirumab Versus Docetaxel and Placebo in the Treatment of Stage IV Non-Small-Cell Lung Cancer Following Disease Progression after One Prior Platinum-Based Therapy (REVEL) study (I4T-MC-JVBA; ClinicalTrials.govNCT01168973). This international, randomized, placebo-controlled, double-blinded phase III trial examines the efficacy and safety of ramucirumab treatment administered in combination with docetaxel, as compared with docetaxel administered with placebo, in patients with stage IV non-small-cell lung cancer (NSCLC) whose disease progressed during or after first-line platinum-based chemotherapy with or without maintenance treatment. The primary end point is overall survival; secondary end points include progression-free survival, objective response rate, disease control rate, patient-reported outcomes, and assessment of safety and tolerability of ramucirumab. Eligible patients (enrollment N = 1242) are randomized at a 1:1 ratio to receive either docetaxel (75 mg/m(2)) plus ramucirumab (10 mg/kg) (Arm A) or docetaxel (75 mg/m(2)) plus placebo (Arm B). Both drugs are administered via intravenous infusion once every 3 weeks until evidence of disease progression, unacceptable toxicity, noncompliance, or patient's consent withdrawal. Efficacy and safety will be compared between the study arms and in patient subgroups including patients with nonsquamous versus squamous tumor histology and patients who received prior bevacizumab treatment. Multiple blood and tumor tissue biomarker samples are collected during the study. The goal of the REVEL study is to demonstrate that ramucirumab in combination with docetaxel improves overall survival of patients with NSCLC with progressive disease after first-line therapy, and to advance our knowledge of the role of angiogenesis blockade in patients with NSCLC by identifying patients who are likely to experience maximum benefit based on extensive clinical biomarker correlative analysis.

Pharmacokinetically guided phase 1 trial of the IGF-1 receptor antagonist RG1507 in children with recurrent or refractory solid tumors

PURPOSE

This pediatric phase I study was designed to identify the doses of RG1507, a monoclonal antibody against the Type 1 Insulin-like Growth Factor Receptor (IGF1R), that achieves exposures equivalent to those achieved in adults at recommended doses.

EXPERIMENTAL DESIGN

Children with relapsed or refractory solid tumors were treated using the same doses and administration schedules of RG1507 (3 and 9 mg/kg/wk, and 16 mg/kg every 3 weeks [q3W]) as those studied in adults. Detailed pharmacokinetic (PK) sampling was performed after the first dose; selected peak and trough levels were subsequently obtained. Target exposures were ≥85% of mean areas under concentration x time curves (AUCs) in adults at doses of 9 mg/kg/wk and 16 mg/kg q3W. A maximum tolerated dose could be identified if dose-limiting toxicities (DLT) occurred.

RESULTS

Thirty-one evaluable patients aged 3-17 years were enrolled at 3 mg/kg/wk (n = 3), 9 mg/kg/wk (n = 18), or 16 mg/kg q3W (n = 10). There were no DLTs. At 9 mg/kg/wk the mean AUC(0-7d) (21,000 μg h/mL) exceeded the target (16,000 μg h/mL). At 16 mg/kg q3W, the mean AUC(021d) (70,000 μg h/mL) exceeded the target (59,400 μg h/mL). Clearance normalized to body weight was age dependent. There were no objective responses. Seven patients had stable disease for >12 weeks, including two patients with osteosarcoma with stable disease for 52+ and 78+ weeks.

CONCLUSIONS

The recommended doses of RG1507 in children with solid tumors are 9 mg/kg/wk and 16 mg/kg q3W. This flexible design is well suited for trials of agents associated with limited toxicity.

Abstract C112: Pharmacokinetically guided phase 1 trial of the IGF-1 receptor antagonist R1507 administered weekly in children with recurrent or refractory solid tumors

R1507 is a fully human monoclonal antibody that binds the IGF-1 receptor (IGF1R) and blocks IGF1R-mediated signal transduction. A phase 1 trial of weekly R1507 in adults did not define a maximum tolerated dose (MTD), and dose-limiting toxicity (DLT) was not observed. This pediatric phase 1 trial of R1507 was designed to identify a dose that achieves a mean area under the concentration x time curve (AUC0–7d) &gt;85% of the mean AUC0–7d (18,700 mcg•h/mL) in adults at the recommended phase 2 dose (RPTD) of 9 mg/kg weekly. The design can define an MTD if DLT occurs. Patients (pts) age &gt;2 and &lt;18 years (y) with relapsed or refractory solid tumors including brain tumors were eligible. Detailed PK sampling was performed after the 1st dose; selected peak and trough levels were obtained to week 10. Nineteen evaluable pts (median age 10 y, range 3–17) with Ewing sarcoma (3), rhabdomyosarcoma (4), adrenocortical carcinoma (2), ependymoma (2), liver tumors (4), or other solid tumors (4) were enrolled. The AUC0-7d (mean 5,670 mcg•h/mL; CV 30%) at the starting dose of 3 mg/kg (n=3) was below the target AUC0-7d, but the AUC0-7d in the first 3 pts treated with 9 mg/kg (mean 22,500 mcg•h/mL) exceeded the target. This cohort was expanded to study 3 age groups: 2–6, 7–11, and 12–17 y. The mean AUC0-7d in the expanded cohort (n=16) was 21,500 mcg•h/mL (CV 25%), but was lower in the 2–6 y cohort (Table) where 2/4 pts did not achieve the target AUC0-7d. In simulations, 300 mg/m2 dosing yielded more uniform drug exposure across the age range (Table). The half-life at 9 mg/kg was 4–8 days. The mean trough concentration on day 35 was 224 mcg/mL. Accumulation was modest (trough35d:trough7d= 2.7). DLT and cumulative toxicity were not observed over a median of 5 weeks of treatment (range 1–44). Toxicities included fatigue, nausea, arthralgia, extremity pain, and anorexia; all were grade &lt;3. Six pts had stable disease ≥12 weeks' duration, including 2 with Ewing's sarcoma and 2 with ependymoma. The recommended R1507 dose is 9 mg/kg weekly in children age &gt; 6 years. Dosing based on body surface area may be preferable for children &lt;6 y.

Single Dose PK Parameter Mean (%CV) Age group Cmax (mcg/mL) CL (mL/day/kg) AUC0–7d (mcg·h/mL) Ctrough, steady state (day 35) (mcg/mL) Simulated AUC0–7d (mcg·h/mL)* 2–6 y 222 (20) 7.1 (15) 17,100 (13) 196 24,800 (n=4) (N/A n=1) 7–11 y 253 (30) 7.0 (27) 20,900 (30) 208 23,000 (n=6) (39; n=5) 12–17 y 293 (16) 5.5 (28) 25,000 (16) 248 24,400 (n=6) (39; n=5) * Simulated AUC0–7d for dosing with 300 mg/m2

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C112.

Regulation of autoreactive antibodies

PURPOSE OF REVIEW

Significant progress has been made over recent years in uncovering the B-cell tolerance mechanisms that control development of autoreactive antibodies. This review examines current knowledge on the regulation and selection of autoreactive B cells in mouse models, and in healthy humans and patients with autoimmune disorders.

RECENT FINDINGS

Autoreactive B cells undergo stringent selection either in the bone marrow or peripheral circulation by deletion, induction of anergy, or receptor editing. There is growing evidence that receptor editing represents the primary physiologic B-cell tolerance mechanism. Several checkpoints against autoreactive B cells have been established in bone marrow and peripheral blood of healthy humans. Recent studies demonstrate that some autoimmune disorders are associated with several alterations in B-cell tolerance checkpoints and often lead to a greater number of autoreactive B cells in the circulation.

SUMMARY

Discovering the precise nature of B-cell tolerance alterations in patients with autoimmune diseases will lead to the identification of new targets for therapeutic interventions in patients with these disorders.

Efficient generation of monoclonal antibodies from single human B cells by single cell RT-PCR and expression vector cloning

We have developed an efficient strategy that combines immunoglobulin (Ig) gene repertoire analysis and Ig reactivity profiling at the single cell level. Based on surface marker expression individual cells at different stages of human B cell development are isolated by fluorescence-activated cell sorting. For each cell Ig heavy and corresponding Ig light chain gene transcripts are amplified by nested RT-PCR and cloned into eukaryotic expression vectors to produce monoclonal human antibodies of the same specificity in vitro. All reactions are performed in 96-well plates and allow cloning of large numbers of Ig genes. The recombinant antibodies are tested for reactivity with diverse self- and non-self antigens and the reactivity profile can be directly linked to the complete Ig heavy and Ig light chain gene sequence information that is obtained as part of the cloning strategy. In summary, our method to clone and express human monoclonal antibodies is unbiased, highly efficient, requires only small cell numbers and the recombinant antibodies allow direct conclusions on the frequency of specific human B cells in a diverse repertoire.

Autoreactivity in human IgG+ memory B cells

More than half of the nascent B cells in humans initially express autoreactive antibodies. However, most of these autoantibodies are removed from the repertoire at two checkpoints before maturation into naive B cells. A third checkpoint excludes remaining autoantibodies from the antigen-experienced IgM(+) memory B cell pool. Nevertheless, low-affinity self-reactive antibodies are frequently found in the serum of normal humans. To determine the source of these antibodies, we cloned and expressed antibodies from circulating human IgG(+) memory B cells. Surprisingly, we found that self-reactive antibodies including anti-nuclear antibodies were frequently expressed by IgG(+) memory B cells in healthy donors. Most of these antibodies were created de novo by somatic hypermutation during the transition between mature naive and IgG(+) memory B cells. We conclude that deregulation of self-reactive IgG(+) memory B cells may be associated with autoimmunity.

Persistent expression of autoantibodies in SLE patients in remission

A majority of the antibodies expressed by nascent B cells in healthy humans are self-reactive, but most of these antibodies are removed from the repertoire during B cell development. In contrast, untreated systemic lupus erythematosus (SLE) patients fail to remove many of the self-reactive and polyreactive antibodies from the naive repertoire. Here, we report that SLE patients in clinical remission continue to produce elevated numbers of self-reactive and polyreactive antibodies in the mature naive B cell compartment, but the number of B cells expressing these antibodies is lower than in patients with active disease. Our finding that abnormal levels of self-reactive mature naive B cells persist in the majority of patients in clinical remission suggests that early checkpoint abnormalities are an integral feature of SLE.

A checkpoint for autoreactivity in human IgM+ memory B cell development

Autoantibodies are removed from the repertoire at two checkpoints during B cell development in the bone marrow and the periphery. Despite these checkpoints, up to 20% of the antibodies expressed by mature naive B cells in healthy humans show low levels of self-reactivity. To determine whether self-reactive antibodies are also part of the antigen-experienced memory B cell compartment, we analyzed recombinant antibodies cloned from single circulating human IgM⁺ memory B cells. Cells expressing antibodies specific for individual bacterial polysaccharides were expanded in the IgM⁺ memory compartment. In contrast, B cells expressing self-reactive and broadly bacterially reactive antibodies were removed from the repertoire in the transition from naive to IgM⁺ memory B cell. Selection against self-reactive antibodies was implemented before the onset of somatic hypermutation. We conclude that a third checkpoint selects against self-reactivity during IgM⁺ memory B cell development in humans.

B-Cell Tolerance Checkpoints in Healthy Humans and Patients with Systemic Lupus Erythematosus

Antibodies are protective effector molecules in the body's immune defense against pathogens. However, if directed against the body's own tissues or organs, antibodies can also play a role in the pathogenesis of autoimmune disease. Here, we discuss our data on how autoreactive antibodies are regulated in healthy humans and how a failure to establish self-tolerance during early B-cell development in patients with systemic lupus erythematosus may predispose to the development of this autoimmune disease.

Defective B cell tolerance checkpoints in systemic lupus erythematosus

A cardinal feature of systemic lupus erythematosus (SLE) is the development of autoantibodies. The first autoantibodies described in patients with SLE were those specific for nuclei and DNA, but subsequent work has shown that individuals with this disease produce a panoply of different autoantibodies. Thus, one of the constant features of SLE is a profound breakdown in tolerance in the antibody system. The appearance of self-reactive antibodies in SLE precedes clinical disease, but where in the B cell pathway tolerance is first broken has not been defined. In healthy humans, autoantibodies are removed from the B cell repertoire in two discrete early checkpoints in B cell development. We found these checkpoints to be defective in three adolescent patients with SLE. 25–50% of the mature naive B cells in SLE patients produce self-reactive antibodies even before they participate in immune responses as compared with 5–20% in controls. We conclude that SLE is associated with abnormal early B cell tolerance.

Predominant autoantibody production by early human B cell precursors

During B lymphocyte development, antibodies are assembled by random gene segment reassortment to produce a vast number of specificities. A potential disadvantage of this process is that some of the antibodies produced are self-reactive. We determined the prevalence of self-reactive antibody formation and its regulation in human B cells. A majority (55 to 75%) of all antibodies expressed by early immature B cells displayed self-reactivity, including polyreactive and anti-nuclear specificities. Most of these autoantibodies were removed from the population at two discrete checkpoints during B cell development. Inefficient checkpoint regulation would lead to substantial increases in circulating autoantibodies.

Efficient gene transfer to hematopoietic progenitor cells using SV40-derived vectors

We used recombinant SV40 (rSV40)-derived vectors to deliver transgenes to human and simian hematopoietic progenitor cells in culture, and in vivo after transduction ex vivo. rSV40 are highly efficient vectors that are made in very high titers. They infect almost all cells, whether resting or dividing. Two rSV40s were used: SV(HBS), carrying hepatitis B surface antigen as a marker; and SV(Aw) carrying IN#33, a single chain Fv antibody against HIV-1 integrase. CD34+ cells derived from human fetal bone marrow (HFBM) and rhesus macaque bone marrow were transduced once with SV(HBS) without selection. On average 60% of colonies derived from transduced CD34+ cells carried and expressed HBsAg, as assessed by PCR and immunochemistry. Transgene carriage persisted following differentiation of transduced rhesus CD34+ cells into T lymphocytes. In an effort to increase the percentage of gene-marked cells, three sequential treatments of CD34+ cells were done using SV(Aw), without selection. Two weeks later, >95% of colonies expressed IN#33. Unselected SV(Aw)-transduced CD34+ cells from HFBM were transplanted into sublethally irradiated SCID mice. Bone marrow harvested 3 months later showed that >50% of bone marrow cells expressed IN#33. This is comparable with the percentage of human cells in these animals' bone marrow as judged by immunostaining for human CD45. The stability and longevity of transduction in this setting suggests that rSV40 vectors integrate into the cellular genome. This possibility was supported by finding that PCR of genomic DNA using primer pairs with one cellular and one viral primer yielded PCR products only in transduced, but not control, cells. These PCR products hybridized with an SV40 DNA fragment. Thus, rSV40 vectors transduce normal human and primate bone marrow progenitor cells effectively without selection, and maintain transgene expression in vivo following reimplantation. Such high efficiency transduction may be useful in treating diseases of CD34+ cells and their derivatives.

Mice transgenic for monocyte-tropic HIV type 1 produce infectious virus and display plasma viremia: a new in vivo system for studying the postintegration phase of HIV replication

To generate an in vivo system for investigating the postintegration phase of HIV-1 replication, mouse lines transgenic for a full-length infectious proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1JR-CSF, were constructed. Leukocytes from two independent JR-CSF transgenic mouse lines produced HIV-1 that infected human PBMCs. Plasma viremia was detected in these mice at levels (mean, >60,000 HIV RNA copies/ml) comparable to those reported for HIV-1-infected individuals. The levels of HIV RNA in these mice increased several-fold after either treatment with the superantigen Staphylococcus enterotoxin B or infection with Mycobacterium tuberculosis. Thus, a provirus encoding a monocyte-tropic HIV-1 strain under the control of its LTR expressed as a transgene in mice can proceed through the postintegration replication phase and produce infectious virus. In addition, the presence of plasma viremia that can be monitored by measuring plasma HIV-1 RNA levels permits these mice to be used to study the impact of different interventions on modulating in vivo HIV-1 production. Therefore, these mice provide a novel manipulable system to investigate the in vivo regulation of HIV-1 production by factors that activate the immune system. Furthermore, this murine system should be useful in delineating the role of human-specific factors in modulating HIV-1 replication and investigating the in vivo therapeutic efficacy of agents that target the postintegration stages of HIV-1 replication.

thy/liv-SCID-hu mice: a system for investigating the in vivo effects of multidrug therapy on plasma viremia and human immunodeficiency virus replication in lymphoid tissues

Modified, human immunodeficiency virus (HIV)-inoculated thy/liv-SCID-hu mice were used to evaluate the in vivo efficacy of antiretroviral drugs. Ritonavir treatment alone initially suppressed plasma viremia, but the viremia recurred with the appearance of ritonavir-resistant HIV isolates. Multidrug therapy suppressed plasma HIV RNA to undetectable levels; however, plasma viremia returned after therapy was stopped, showing that the therapy did not completely suppress HIV infection in the thymic implant. When thy/liv-SCID-hu mice were treated with a combination of zidovudine, lamivudine, and ritonavir immediately after inoculation with HIV, cocultures of the thymic implants remained negative for HIV even 1 month after therapy was discontinued, suggesting that acute treatment can prevent the establishment of HIV infection. Thus, these modified thy/liv-SCID-hu mice should prove to be a useful system for evaluating the effectiveness of different antiretroviral therapies on acute and chronic HIV infection.

Mice transgenic for human CD4 and CCR5 are susceptible to HIV infection

HIV entry into human cells is mediated by CD4 acting in concert with one of several members of the chemokine receptor superfamily. The resistance to HIV infection observed in individuals with defective CCR5 alleles indicated that this particular chemokine receptor plays a crucial role in the initiation of in vivo HIV infection. Expression of human CD4 transgene does not render mice susceptible to HIV infection because of structural differences between human and mouse CCR5. To ascertain whether expression of human CD4 and CCR5 is sufficient to make murine T lymphocytes susceptible to HIV infection, the lck promoter was used to direct the T cell-specific expression of human CD4 and CCR5 in transgenic mice. Peripheral blood mononuclear cells and splenocytes isolated from these mice expressed human CD4 and CCR5 and were infectible with selected M-tropic HIV isolates. After in vivo inoculation, HIV-infected cells were detected by DNA PCR in the spleen and lymph nodes of these transgenic mice, but HIV could not be cultured from these cells. This indicated that although transgenic expression of human CD4 and CCR5 permitted entry of HIV into the mouse cells, significant HIV infection was prevented by other blocks to HIV replication present in mouse cells. In addition to providing in vivo verification for the important role of CCR5 in T lymphocyte HIV infection, these transgenic mice represent a new in vivo model for understanding HIV pathogenesis by delineating species-specific cellular factors required for productive in vivo HIV infection. These mice should also prove useful for the assessment of potential therapeutic and preventative modalities, particularly vaccines.

Saquinavir-mediated inhibition of human immunodeficiency virus (HIV) infection in SCID mice implanted with human fetal thymus and liver tissue: an in vivo model for evaluating the effect of drug therapy on HIV infection in lymphoid tissues

Treatment with protease inhibitors alone or in combination with inhibitors of reverse transcriptase potently suppresses levels of human immunodeficiency virus (HIV) RNA in plasma and thereby may significantly delay the progression of HIV-mediated disease. To investigate the effect of treatment with the protease inhibitor saquinavir on HIV replication in the lymphoid tissues, we used a SCID-hu mouse model that we developed, in which human thymic and liver tissues (hu-thy/liv) were implanted under both kidney capsules in SCID mice (thy/liv-SCID-hu mice). These mice are populated in the periphery with large numbers of human T cells and develop disseminated HIV infection after intraimplant injection. thy/liv-SCID-hu mice with established HIV infection that were treated for 1 month with saquinavir had a significantly lower viral load present in the implanted hu-thy/liv and mouse spleen than did the untreated HIV-infected thy/liv-SCID-hu mice. To examine the capacity of acute treatment with saquinavir to prevent HIV infection, some thy/liv-SCID-hu mice were inoculated with HIV and then immediately started on saquinavir. Although treated mice had markedly lower viral loads in the thy/liv implants and spleens, HIV infection was not completely prevented. Thus, the effect of antiviral therapy on HIV infection in the major site of HIV replication, the lymphoid tissues, can be readily evaluated in our thy/liv-SCID-hu mice. These mice should prove to be a useful model for determining the in vivo effectiveness of different therapeutic interventions on acute and chronic HIV infection.

Severe combined immunodeficiency mice engrafted with human T cells, B cells, and myeloid cells after transplantation with human fetal bone marrow or liver cells and implanted with human fetal thymus: a model for studying human gene therapy

To develop an in vivo model wherein human hematopoiesis occurs, we transplanted severe combined immunodeficiency (SCID) mice with either human fetal bone marrow (HFBM) or human fetal liver (HFL). After transplantation of SCID mice with cultured HFBM (BM-SCID-hu mice) or HFL cells (Liv-SCID-hu mice), significant engraftment of the mouse bone marrow (BM) and population of the peripheral blood with human leukocytes was detected. Human colony-forming unit-granulocyte macrophage and burst forming unit-erythroid were detected in the BM of the BM-SCID-hu and Liv-SCID-hu mice up to 8 months after transplantation. When the HFBM or HFL cells were transduced with a retroviral vector before transplantation, integrated retroviral sequences were detected in human precursor cells present in the SCID mouse BM and in leukocytes circulating in the peripheral blood (PB) up to 7 months after transplantation. The PB of the BM-SCID-hu mice also became populated with human T cells after implantation with human thymic tissue, which provided a human microenvironment wherein human pre-T cells from the BM could mature. When the HFBM was retrovirally transduced before transplantation, integrated retrovirus was detected in sorted CD4+CD8+ double positive and CD4+ single positive cells from the thymic implant and CD4+ cells from the PB. Taken together, these data indicated that the BM of our BM-SCID-hu and Liv-SCID-hu mice became engrafted with retrovirally transduced human hematopoietic precursors that undergo the normal human hematopoietic program and populate the mouse PB with human cells containing integrated retroviral sequences. In addition to being a model for studying in vivo human hematopoiesis, these mice should also prove to be a useful model for investigating in vivo gene therapy using human stem/precursor cells.

SCID-hu mice: a model for studying disseminated HIV infection

Modifications that we introduced into the implantation of human fetal thymus and liver into SCID mice (thy/liv-SCID-hu mice) markedly increased the population of human T cells and monocytes present in the peripheral blood and peripheral lymphoid compartment of these mice. As a result, the modified thy/liv-SCID-hu mice developed disseminated HIV infection after intraimplant or i.p. inoculation. After chronic HIV infection of these mice, depletion of the peripheral human T cells was observed as reported in HIV-infected individuals. In addition, these mice also developed plasma viremia after infection with HIV. The peripheral blood mononuclear cells were responsive to in-vivo cytokine regulation as evidenced by induction of human IFN-gamma gene expression by human IL-12 and inhibition by human IL-10. Acute treatment with human IL-10 but not with human IL-12 inhibited the development of plasma viremia and HIV infection in thy/liv-SCID-hu mice inoculated with HIV-1(59), a clinical isolate. SCID mice transplanted with cultured human fetal bone marrow displayed significant engraftment of the mouse bone marrow with human precursor cells and population of the peripheral blood with human B cells and monocytes. The peripheral blood of these bone marrow-transplanted SCID mice also became populated with human T cells after they were implanted with human thymic tissue due to migration of human precursor cells from the mouse bone marrow to the implanted human thymus. Thus, these modified SCID-hu mice should prove to be a valuable in-vivo model for studying the immunopathogenesis of HIV infection and for examining the in-vivo efficacy of immunomodulatory, drug and gene therapy in modifying HIV infection.