Abstract 2693: Combining ulixertinib (ERK1/2 Inhibitor) with EGFR and BRAF inhibition yields significant efficacy in preclinical BRAFV600E mutant colorectal cancer models

The BRAFV600E mutation occurs in approximately 7% of colorectal cancer (CRC). BRAF plus EGFR inhibition (encorafenib with cetuximab) is an FDA approved treatment option for adult patients with metastatic CRC. Ultimately, patients develop resistance leading to disease progression. The addition of a MEK inhibitor, binimetinib, did not confer overall survival benefit. We hypothesized that addition of ERK inhibition would increase magnitude and duration of response to BRAF plus EGFR inhibition by overcoming MAPK-related acquired resistance mechanisms. ERK is the terminal master regulator kinase of the RAS-MAPK pathway, therefore, targeting this node is likely to be effective in the context of numerous mechanisms of acquired resistance that reactivate the MAPK pathway.

Ulixertinib (BVD-523) is a first-in-class and best-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other therapeutics. Ulixertinib has demonstrated efficacy in patients with tumors harboring alterations within the RAS-MAPK pathway. The efficacy of ulixertinib, in combination with EGFR inhibition (cetuximab), plus BRAF inhibition (encorafenib), was assessed in CRC cell line derived xenograft models harboring BRAFV600E mutations. The triple combination resulted in superior tumor growth inhibition compared to dosing of any single agent or doublet. RNA sequencing was performed on treated tumor samples. Expression of the mutant BRAF allele was readily confirmed from RNA sequencing data. Gene expression analysis showed differential expression of MAPK pathway genes in triple combination treated groups versus single or doublet therapy.

A complete response to ulixertinib in combination with cetuximab and encorafenib for the treatment of a patient with metastatic CRC has been reported (Stuhlmiller, Timothy Joseph, et al. "Updated clinical outcomes from ULI-EAP-100, an intermediate expanded access program for ulixertinib (BVD-523)." (2022): e15101-e15101). The patient was treated under the Expanded Access Protocol (NCT04566393) for compassionate use access to ulixertinib. Preclinical data and clinical complete response warrants further investigation of ulixertinib plus BRAF and EGFR inhibition.

Citation Format: Deborah Knoerzer, Anupama Reddy, Jessica A. Box, Anna Groover, Brent Kreider, Martin Teresk, Caroline M. Emery. Combining ulixertinib (ERK1/2 Inhibitor) with EGFR and BRAF inhibition yields significant efficacy in preclinical BRAFV600E mutant colorectal cancer models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2693.

Abstract 2692: The combination of ulixertinib (ERK1/2 Inhibitor) and KRASG12C inhibition demonstrates significant efficacy in preclinical models

Ulixertinib (BVD-523) is a first-in-class and best-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other therapeutics. Ulixertinib has demonstrated efficacy in patients with tumors harboring alterations within the RAS-MAPK pathway. KRAS is the most frequently mutated oncogene in cancer and is a key mediator of the RAS-MAPK signaling pathway resulting in proliferation and cellular growth. The specific KRASG12C mutation occurs in approximately 10% of non-small cell lung cancer (NSCLC), 3% of colorectal cancer, and 1-2% across all other tumor types. KRASG12C mutant-inhibitors, including AMG-510 (sotorasib), MRTX849 (adagrasib), and JDQ443 have demonstrated efficacy in KRASG12C-mutant cancers, including NSCLC. Clinically described mechanisms of acquired resistance to KRASG12C inhibitors converge on reactivation of the RAS-MAPK pathway. We hypothesized combining ulixertinib with a KRASG12C inhibitor would circumvent resistance to single agent KRASG12C inhibition, generating increased magnitude and duration of response compared to either single agent alone.

The efficacy of ERK1/2 inhibitor, ulixertinib, in combination with KRASG12C inhibitor, adagrasib, was assessed in cell line derived xenograft models harboring KRASG12C mutations. Models were selected based on response to single agent adagrasib, ranging from sensitive to partially responsive. Combination treatment resulted in superior tumor growth inhibition compared to dosing of either single agent. RNA sequencing was performed on tumor samples that were collected 2 hours after the last dose of treatment. Expression of the mutant KRAS alleles were readily confirmed from RNA sequencing data in all models. Gene expression analysis showed differential expression of MAPK pathway genes in monotherapy versus combination therapy treated groups.

In summary, ulixertinib combined with adagrasib exhibited robust pre-clinical activity in a variety of xenograft models with KRASG12C and should be further evaluated.

Citation Format: Deborah Knoerzer, Anupama Reddy, Jessica A. Box, Anna Groover, Brent Kreider, Martin Teresk, Caroline M. Emery. The combination of ulixertinib (ERK1/2 Inhibitor) and KRASG12C inhibition demonstrates significant efficacy in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2692.

Phase Ib Study of Ulixertinib Plus Gemcitabine and Nab-Paclitaxel in Patients with Metastatic Pancreatic Adenocarcinoma

BACKGROUND

Ulixertinib is a novel oral ERK inhibitor that has shown promising single-agent activity in a phase I clinical trial that included patients with RAS-mutant cancers.

METHODS

We conducted a phase Ib trial combining ulixertinib with gemcitabine and nab-paclitaxel (GnP) for untreated metastatic pancreatic adenocarcinoma. The trial comprised a dose de-escalation part and a cohort expansion part at the recommended phase II dose (RP2D). Primary endpoint was to determine the RP2D of ulixertinib plus GnP and secondary endpoints were to assess toxicity and safety profile, biochemical and radiographic response, progression-free survival (PFS) and overall survival (OS).

RESULTS

Eighteen patients were enrolled. Ulixertinib 600 mg PO twice daily (BID) with GnP was initially administered but was de-escalated to 450 mg BID as RP2D early during dose expansion due to poor tolerability, which ultimately led to premature termination of the study. Common treatment-related adverse events (TRAEs) were anemia, thrombocytopenia, rash and diarrhea. For 5 response evaluable patients, one patient achieved a partial response and 2 patients achieved stable disease. For 15 patients who received the triplet, median PFS and OS were 5.46 and 12.23 months, respectively.

CONCLUSION

Ulixertinib plus GnP had similar frequency of grade ≥3 TRAEs and potentially efficacy as GnP, however was complicated by a high rate of all-grade TRAEs (ClinicalTrials.gov Identifier: NCT02608229).

Paediatric Strategy Forum for medicinal product development in mitogen-activated protein kinase pathway inhibitors: ACCELERATE in collaboration with the European Medicines Agency with participation of the Food and Drug Administration

As the mitogen-activated protein kinase (MAPK) signalling pathway is activated in many paediatric cancers, it is an important therapeutic target. Currently, a range of targeted MAPK pathway inhibitors are being developed in adults. However, MAPK signals through many cascades and feedback loops and perturbing the MAPK pathway may have substantial influence on other pathways as well as normal development. In view of these issues, the ninth Paediatric Strategy Forum focused on MAPK inhibitors. Development of MAPK pathway inhibitors to date has been predominantly driven by adult indications such as malignant melanoma. However, these inhibitors may also target unmet needs in paediatric low-grade gliomas, high-grade gliomas, Langerhans cell histiocytosis, juvenile myelomonocytic leukaemia and several other paediatric conditions. Although MAPK inhibitors have demonstrated activity in paediatric cancer, the response rates and duration of responses needs improvement and better documentation. The rapid development and evaluation of combination approaches, based on a deep understanding of biology, is required to optimise responses and to avoid paradoxical tumour growth and other unintended consequences including severe toxicity. Better inhibitors with higher central nervous systempenetration for primary brain tumours and cancers with a propensity for central nervous system metastases need to be studied to determine if they are more effective than agents currently being used, and the optimum duration of therapy with MAPK inhibition needs to be determined. Systematic and coordinated clinical investigations to inform future treatment strategies with MAPK inhibitors, rather than use outside of clinical trials, are needed to fully assess the risks and benefits of these single agents and combination strategies in both front-line and in the refractory/relapse settings. Platform trials could address the investigation of multiple similar products and combinations. Accelerating the introduction of MAPK inhibitors into front-line paediatric studies is a priority, as is ensuring that these studies generate data appropriate for scientific and regulatory purposes. Early discussions with regulators are crucial, particularly if external controls are considered as randomised control trials in small patient populations can be challenging. Functional end-points specific to the populations in which they are studied, such as visual acuity, motor and neuro psychological function are important, as these outcomes are often more reflective of benefit for lower grade tumours (such as paediatric low-grade glioma and plexiform neurofibroma) and should be included in initial study designs for paediatric low-grade glioma. Early prospective discussions and agreements with regulators are necessary. Long-term follow-up of patients receiving MAPK inhibitors is crucial in view of their prolonged administration and the important involvement of this pathway in normal development. Further rational development, with a detailed understanding of biology of this class of products, is crucial to ensure they provide optimal benefit while minimising toxicity to children and adolescents with cancer.

Abstract 5221: The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics

Ulixertinib (BVD-523) is a well-tolerated, orally delivered, catalytic ERK1/2 inhibitor, which has shown promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Pediatric low grade gliomas (pLGGs) are the most common pediatric brain tumors, with the most frequent driving alterations (KIAA:BRAF fusion, BRAF V600E mutation) occurring in the MAPK pathway.

To investigate the anti-tumoral activity of ulixertinib in pLGG, cell lines recapitulating both main MAPK alterations were used: DKFZ-BT66 (pilocytic astrocytoma; KIAA:BRAF fusion) and BT40 (pleomorphic xanthoastrocytoma; BRAF V600E mutation and CDKN2A/B deletion). The potential synergism of combinations with MEK inhibitors, senolytics, and chemotherapy was investigated in vitro using metabolic activity and MAPK activity assays. The most promising combinations were validated in vitro by analysis of viable, dead, and apoptotic cells through high-content microscopy. The most clinically relevant combinations were further validated in vivo: 1) in two zebrafish embryo models (respectively, BT40 and DKFZ-BT66 yolk sac injection) and 2) in NSG mice (BT40 orthotopic PDX) including in vivo pharmacokinetic and -dynamic analyses.

Our data demonstrate ulixertinib’s ability to inhibit MAPK pathway activity in all used models. Ulixertinib treatment reduced cell viability in the BRAF V600E mutated cell line at a remarkably low concentration of 62.7 nM (compared to other cell lines’ IC50 from the Genomics of Drug Sensitivity in Cancer database). In vivo pharmacokinetic and -dynamic analyses showed good penetrance of the drug into mouse brain tissue, with concentrations above the in vitro IC50 and reduction of MAPK activity as assessed by Western blot. Furthermore, ulixertinib treatment slowed tumor growth and significantly increased survival in NSG mice with orthotopic BT40 xenografts.

Ulixertinib showed indications for anti-proliferative synergy in vitro, according to the Loewe and Bliss independence models, in combination with MEK inhibitors (trametinib, binimetinib) or senolytics (navitoclax, A1331852). Combinations with chemotherapy (carboplatin, vinblastine) were at most additive. Indications for synergy with binimetinib and navitoclax were confirmed in the zebrafish embryo xenograft models for both MAPK-altered backgrounds. The combination of ulixertinib with navitoclax was further investigated in the BT40 PDX mouse model, where tumor growth and survival were comparable to ulixertinib monotherapy.

In conclusion, our data indicate a strong potential for ulixertinib as a clinically relevant therapeutic option for the treatment of pLGG to be further investigated in upcoming clinical trials. Potential synergism with MEK inhibitors and senolytics was noted and warrants further investigation.

Citation Format: Romain Sigaud, Lisa Rösch, Charlotte Gatzweiler, Julia Benzel, Laura von Soosten, Heike Peterziel, Sara Najafi, Simay Ayhan, Nina Hofmann, Kathrin I. Förster, Jürgen Burhenne, Rémi Longuespée, Cornelis M. van Tilburg, David T. Jones, Stefan M. Pfister, Deborah Knoerzer, Brent Kreider, Max Sauter, Kristian W. Pajtler, Marc Zuckermann, Ina Oehme, Olaf Witt, Till Milde. The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5221.

Abstract 1057: Significant efficacy demonstrated with the combination of ulixertinib (ERK1/2 inhibitor) and CDK4/6 inhibitors in MAPK altered models

Ulixertinib (BVD-523) is a first-in-class small molecule inhibitor of ERK1/2 currently being investigated in several oncology clinical trials, both as a single agent and in combination with other anti-cancer therapeutics. Palbociclib and ribociclib are FDA approved orally active, potent, and highly selective reversible inhibitors of the CDK4 and CDK6 kinases. As it is well established that ERK activation increases cyclin D levels and entry into the cell cycle, we hypothesized that the combination of ERK1/2 and CDK4/6 inhibition would have synergistic antitumor activity and cause tumor regression in vivo.

Initial in vitro work combined ulixertinib with CDK4/6 inhibitors across a small panel of lung cancer cell lines. Cell lines carrying a KRAS mutation were more sensitive to ulixertinib relative to KRAS wild type cell lines based on single agent IC50 values. The single agent IC50 values for the CDK4/6 inhibitors were dependent on whether a metabolic or non-metabolic readout for cell viability was used. The combination interactions across a dose matrix of concentrations were determined by the Loewe Additivity and Bliss Independence models. The results of combining ulixertinib and CDK4/6 inhibitors ranged from additive to potentially synergistic.

The combination of ulixertinib and palbociclib was then assessed against four xenograft models representing colorectal, melanoma, and pancreatic tumor types, each harboring an alteration within a component of the MAPK pathway. Palbociclib monotherapy across all models showed limited tumor growth inhibition (TGI) while ulixertinib monotherapy demonstrated modest TGI across all models. The combination groups demonstrated significant responses ranging from 75% - 90% TGIs. All treatment regimens were well tolerated across all models. Downstream assays were completed including reverse phase protein arrays (RPPA). Using RPPA, treatment effects on protein signaling was evaluated in the MAPK family, cell cycle regulation, and other associated feedback and compensatory pathways. Notably, suppression of protein targets downstream of ERK1/2 were seen with both ulixertinib monotherapy and combination therapy. Similarly, the combination therapy group reduced protein levels involved in cell cycle progression, which was not seen in either monotherapy group alone.

The efficacy demonstrated with this preclinical work has proven to be translatable to the clinic as the combination of ulixertinib and palbociclib recently achieved MTD in a Phase I trial in advanced solid tumors including pancreatic cancer (NCT 03454035).

Citation Format: Caroline M. Emery, Brian Corgiat, Justin Davis, David Sorrell, Mitch Johnson, Brent Kreider, Deborah Knoerzer. Significant efficacy demonstrated with the combination of ulixertinib (ERK1/2 inhibitor) and CDK4/6 inhibitors in MAPK altered models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1057.

LGG-25. The first-in-class ERK inhibitor ulixertinib (BVD-523) shows activity in MAPK-driven pediatric low-grade glioma models as single agent and in combination with MEK inhibitors or senolytics

Ulixertinib (BVD-523) is a catalytic ERK1/2 inhibitor that showed promising responses in adult patients with mitogen-activated protein kinase (MAPK)-driven solid tumors. Pediatric low-grade gliomas (pLGG) are the most common pediatric brain tumors, with the most frequent driving alterations in the MAPK pathway. The anti-tumor activity of ulixertinib in pLGG and its potential synergism in combination with MEK inhibitors, senolytics, and chemotherapy were investigated in vitro using metabolic activity, MAPK reporter assay and high-content microscopy in pLGG-derived cell lines (DKFZ-BT66 - KIAA:BRAF fusion; BT40 - BRAF V600E mutation and CDKN2A/B deletion). The most clinically relevant combinations were further validated in vivo: 1) in zebrafish embryo models (BT40 and DKFZ-BT66 yolk sac injection) and 2) in NSG mice (BT40 orthotopic PDX) including in vivo pharmacokinetic and -dynamic analyses. Ulixertinib inhibited MAPK pathway activity in all models and reduced cell viability in the BRAF V600E mutated cell line at concentrations in the nanomolar range. In vivo pharmacokinetic and -dynamic analyses showed penetrance of the drug into mouse brain tissue and on-target activity, with concentrations above the in vitro IC50 and reduction of MAPK activity. Ulixertinib treatment slowed tumor growth and significantly increased survival in NSG mice with BT40 xenografts. Ulixertinib showed indications for anti-proliferative synergy in vitro in combination with MEK inhibitors (trametinib, binimetinib) or BH3 mimetics (navitoclax, A-1331852). Combinations with chemotherapy (carboplatin, vinblastine) were at most additive. Indications for synergy with binimetinib and navitoclax were confirmed in the zebrafish embryo models. In the NSG mouse model, the combination of ulixertinib with senolytics induced effects on tumor growth and survival comparable to ulixertinib monotherapy. Ulixertinib shows promising potential as a clinically relevant therapeutic option for the treatment of pLGG to be further investigated in upcoming clinical trials. Potential synergism with MEK inhibitors and BH3 mimetics was noted and warrants further investigation.

Clinical characteristics and treatment outcomes in patients with histiocytic neoplasms harboring class 3 MAP2K1 mutations, including treatment with the ERK inhibitor ulixertinib

e19081

Background: Histiocytic neoplasms (HN) are clonal myeloid disorders with diverse clinical phenotypes. HN nearly invariably harbor mutations of the mitogen activated protein kinase (MAPK) pathway, including the BRAFV600E mutation in HN subtypes that are responsive to BRAF inhibition. More recently characterized, the second most frequently mutated gene driving HN is MAP2K1, with broad responsiveness to MEK inhibition reported. The most common MAP2K1 variant observed in our cohort (n=300 patients) is the exon 3 p.E102_I103 in-frame deletion, among the Class 3 MAP2K1 mutants predicted to be resistant to allosteric MEK inhibition. We present clinical and treatment characteristics of HN patients with Class 3 MAP2K1 mutations. Methods: Patients with HN and exon 3 p.E102_I103del or similar mutations identified by tumor sequencing were included. Sites of disease were captured. First- and later-line treatments were categorized as observation, chemotherapy (vinblastine, cytarabine, cladribine, methotrexate), immune modulation (anakinra or interferon), MEK inhibition (trametinib or cobimetinib), or ERK inhibition (ulixertinib). Clinical and radiologic responses were captured as partial response (PR), complete response (CR), or progressive disease (PD). PD includes relapse following PR or CR. Results: 16 patients were identified. 8 (50%) were female, and median age at HN diagnosis was 31 (range 22-58). 10 patients had Langerhans cell histiocytosis (LCH), 4 had Erdheim-Chester disease (ECD), 2 had mixed histiocytosis. Sites of HN were bone (16; 100%), lymph node (8; 50%), brain (8; 50%), skin/subcutaneous (4; 25%), retroperitoneum (3; 19%), cardiovascular (3; 19%), abdomen (2; 13%), reproductive (1; 6%) and other sites (5; 31%). Mutations identified were MAP2K1 p.E102_103del (13; 81%), p.L101_103delinsF (1; 6%), p.P105_I107delinsL (1; 6%), and p.I103_A106del (1; 6%). 2 (13%) patients had spontaneous regression of disease and were observed; 3 (19%) patients had CR to first-line chemotherapy. 3 (19%) patients have had CR/PR to first-line MEK inhibition. 8 (50%) patients had PD following chemotherapy and/or immune modulation; of those, 1 was lost to follow-up, 4 had CR/PR to MEK inhibition; however, 3 had PD despite MEK inhibition. These three patients and one treatment-naïve patient were treated with an oral ERK1/2 inhibitor, ulixertinib, on prospective protocols. 3 of 4 had a clinical or radiologic PR (1) or CR (2). Conclusions: Histiocytic neoplasms with Class 3 MAP2K1 mutations represent a diverse spectrum of disease characterized by frequent bone, nodal and neurologic involvement, by frequent resistance to chemotherapy. This entity is resistant to MEK inhibition in some patients, a phenomenon previously undocumented, and responsive to ERK inhibition, which may be a promising therapeutic approach to HN.

A two-part, phase II, multi-center study of the ERK inhibitor ulixertinib (BVD-523) for patients with advanced malignancies harboring MEK or atypical BRAF alterations (BVD-523-ABC)

TPS3172

Background: Ulixertinib (BVD-523) is a small molecule inhibitor of extracellular signal-regulated kinases 1/2 (ERK1/2) in development as a novel anti-cancer drug. Early clinical data demonstrated anti-tumor activity, especially for patients with tumors harboring atypical BRAF or MEK1/2 alterations (Sullivan et al., Cancer Discov. 2018;8(2):184-195). Atypical BRAF (non-V600) alterations can be categorized according to characteristics of molecular signaling (Class II or III), are seen in approximately 3% of all human cancers, and there are currently no approved therapies for this indication. Similar to atypical BRAF alterations, the incidence of MEK1/2 alterations are rare in human tumors (< 1 %). Preclinical data have demonstrated activity of ulixertinib in MEK mutant models. Ulixertinib has FDA fast-track designation for patients with solid tumors, other than CRC, with specific BRAF mutations (G469A, L485W, or L597Q). Designed with intent to register, the BVD-523-ABC clinical trial will continue evaluation of ulixertinib in patients with tumors harboring any atypical BRAF or MEK1/2 alteration (NCT04488003). Methods: This multi-center, phase II study, will be conducted in two parts and assess the clinical benefit, safety, pharmacokinetics, and pharmacodynamics of ulixertinib in patients with advanced malignancies. Ulixertinib will be administered at the RP2D of 600 mg BID for 28-day treatment cycles. Eligible patients will have locally advanced or metastatic cancer which progressed following standard systemic therapies, or for which the patient is not a candidate or refused systemic therapy. Planned correlative analyses include reverse phase protein array and transcriptomics of tumor tissue. Part A is open-label and tumor agnostic, except for group 4 and 6 (CRC patients only). Patients will enroll into one of six groups based on BRAF (groups 1-4) or MEK1/2 (groups 5-6) tumor alteration (38 patients per group). Overall response rate (ORR) is the primary endpoint for Part A, with secondary endpoints including duration of response (DOR), progression-free survival (PFS), and overall survival (OS). Part B is tumor histology specific. Patients will be randomized to receive either ulixertinib or physician's choice of treatment in a 2:1 ratio. Up to three specified tumor histologies will be defined, guided by available Part A data (n = 80-100 per histology). The primary endpoint of Part B is PFS, and secondary endpoints include OS, ORR, and DOR. This study has enrolled 43 patients of the planned 228 in Part A at the time of abstract submission. Clinical trial information: NCT04488003.

Intratumoral Injection of Clostridium novyi-NT Spores in Patients with Treatment-refractory Advanced Solid Tumors

PURPOSE

Intratumorally injected Clostridium novyi-NT (nontoxic; lacking the alpha toxin), an attenuated strain of C. novyi, replicates within hypoxic tumor regions resulting in tumor-confined cell lysis and inflammatory response in animals, which warrants clinical investigation.

PATIENTS AND METHODS

This first-in-human study (NCT01924689) enrolled patients with injectable, treatment-refractory solid tumors to receive a single intratumoral injection of C. novyi-NT across 6 dose cohorts (1 × 10⁴ to 3 × 10⁶ spores, 3+3 dose-escalation design) to determine dose-limiting toxicities (DLT), and the maximum tolerated dose.

RESULTS

Among 24 patients, a single intratumoral injection of C. novyi-NT led to bacterial spores germination and the resultant lysis of injected tumor masses in 10 patients (42%) across all doses. The cohort 5 dose (1 × 10⁶ spores) was defined as the maximum tolerated dose; DLTs were grade 4 sepsis (n = 2) and grade 4 gas gangrene (n = 1), all occurring in three patients with injected tumors >8 cm. Other treatment-related grade ≥3 toxicities included pathologic fracture (n = 1), limb abscess (n = 1), soft-tissue infection (n = 1), respiratory insufficiency (n = 1), and rash (n = 1), which occurred across four patients. Of 22 evaluable patients, nine (41%) had a decrease in size of the injected tumor and 19 (86%) had stable disease as the best overall response in injected and noninjected lesions combined. C. novyi-NT injection elicited a transient systemic cytokine response and enhanced systemic tumor-specific T-cell responses.

CONCLUSIONS

Single intratumoral injection of C. novyi-NT is feasible. Toxicities can be significant but manageable. Signals of antitumor activity and the host immune response support additional studies of C. novyi-NT in humans.

The effect of dental insurance on the use of dental care for older adults: a partial identification analysis

We evaluate the impact of dental insurance on the use of dental services using a potential outcomes identification framework designed to handle uncertainty created by unknown counterfactuals-that is, the endogenous selection problem-and uncertainty about the reliability of self-reported insurance status. Using data from the health and retirement study, we estimate that utilization rates of adults older than 50 years would increase from 75% to around 80% under universal dental coverage.

Bounding the effects of food insecurity on children's health outcomes

Previous research has estimated that food insecure children are more likely to suffer from a wide array of negative health outcomes than food secure children, leading many to claim that alleviating food insecurity would lead to better health outcomes. Identifying the causal impacts is problematic, however, given endogenous selection into food security status and potential mismeasurement of true food security status. Using recently developed nonparametric bounding methods and data from the 2001-2006 National Health and Nutritional Examination Survey (NHANES), we assess what can be identified about the effects of food insecurity on child health outcomes in the presence of nonrandom selection and nonclassical measurement error. Under relatively weak monotonicity assumptions, we can identify that food security has a statistically significant positive impact on favorable general health and being a healthy weight. Our work suggests that previous research has more likely underestimated than overestimated the causal impacts of food insecurity on health.

Analysis of eosinophils and myeloid progenitor responses to modified forms of MPIF-2

Myeloid progenitor inhibitory factor (MPIF)-2 is a beta-chemokine with select and potent activities on eosinophils and myeloid progenitors. In the beta-chemokine family, biological activity is modulated by differential processing of the amino-terminus. Here, for MPIF-2, we describe the biological activities of NH(2)-terminal deletion mutants and compare regions necessary for eosinophil and myeloid progenitor activities. Five MPIF-2 proteins with deletions at the amino-terminus were produced in Escherichia coli and assayed for calcium mobilization, chemotaxis and receptor binding activities on eosinophils, and for their ability to inhibit colony formation of human myeloid bone marrow progenitors. For eosinophils, deletion of the first two amino acids did not markedly alter activity, while subsequent truncations result in a complete loss of activity. One of the MPIF-2 mutants, MPIF-2 (P30-R99) was converted from an agonist to an antagonist of eotaxin, MPIF-2 and MCP-4 functional responses in eosinophil calcium flux and chemotaxis assays. Surprisingly, while displaying a complete loss of agonist activity toward eosinophils, MPIF-2 (P30-R99) retains ability to inhibit human bone marrow myeloid progenitor cell colony formation. In addition, processing at the amino terminus of MPIF-2 in vivo, may result in a chemokine with altered biological activities.

Identification and characterization of a new human ETS-family transcription factor, TEL2, that is expressed in hematopoietic tissues and can associate with TEL1/ETV6

The ETS family of proteins is a large group of transcription factors implicated in many aspects of normal hematopoietic development, as well as oncogenesis. For example, the TEL1/ETV6 (TEL1) gene is required for normal yolk sac angiogenesis, adult bone marrow hematopoiesis, and is rearranged or deleted in numerous leukemias. This report describes the cloning and characterization of a novel ETS gene that is highly related to TEL1 and is therefore called TEL2. The TEL2 gene consists of 8 exons spanning approximately 21 kilobases (kb) in human chromosome 6p21. Unlike the ubiquitously expressed TEL1 gene, however, TEL2 appears to be expressed predominantly in hematopoietic tissues. Antibodies raised against the C-terminus of the TEL2 protein were used to show that TEL2 localizes to the nucleus. All ETS proteins can bind DNA via the highly conserved ETS domain, which recognizes a purine-rich DNA sequence with a GGAA core motif. DNA binding assays show that TEL2 can bind the same consensus DNA binding sequence recognized by TEL1/ETV6. Additionally, the TEL2 protein is capable of associating with itself and with TEL1 in doubly transfected Hela cells, and this interaction is mediated through the pointed (PNT) domain of TEL1. The striking similarities of TEL2 to the oncogenic TEL1, its expression in hematopoietic tissues, and its ability to associate with TEL1 suggest that TEL2 may be an important hematopoietic regulatory protein.

Quantification of the effects of astrocytes on oligodendroglial morphology

Oligodendrocytes in neonatal rat forebrain cultures grow either in isolation of other cells or upon astrocytes. Populations of both types of oligodendrocytes were used to quantify the effects of astrocytes on oligodendroglial morphology. Changes in oligodendroglial size and shape were determined by measurement of total process length, cell area, growth area, and fractal dimension. The directionality of process growth, quantified by measurement of the axes of growth, was also compared. Isolated oligodendrocytes exhibited greater total process length, greater cellular area, larger growth area, and a more complex boundary than oligodendrocytes growing upon astrocytes. Analysis of the axes of cellular growth revealed that the processes of isolated oligodendrocytes exhibited radial symmetry, whereas the processes of oligodendrocytes growing upon astrocytes were limited to an area demarcated by the astrocytic processes. These data suggest that, in neuron-free culture, the growth of oligodendroglial processes is modified by underlying astrocytic processes.

Basic fibroblast growth factor prevents cAMP-induced apoptosis in cultured Schwann cells

Peripheral nerve axotomy induces apoptosis in Schwann cell precursors; basic fibroblast growth factor (bFGF) protects these cells from axotomy-induced apoptosis (Jessen et al.: Neuron 12:509-527, 1994; Gavrilovic et al.: Eur J Neurosci 7:7-85, 1995). In this study, we investigate the effects of bFGF on apoptosis in neuron-free cultures of neonatal rat Schwann cells. Apoptotic cell death was induced in primary and secondary expanded Schwann cells by treatment with 1 mM concentrations of 8-bromoadenosine 3':5'-cyclic monophosphate (8-bromo-cAMP), a membrane-permeable analogue of cAMP which induces expression of galactocerebroside in the plasma membranes of Schwann cells. Treatment with bFGF reduced the percentage of galactocerebroside-bearing Schwann cells undergoing cAMP-induced DNA fragmentation. These findings suggest that bFGF can enhance the survival of terminally differentiated Schwann cells by preventing apoptosis.

Health insurance and the homeless

There is very little known about health care utilization among the homeless or about the role of health insurance on utilization patterns. Many health care reform proposals advocate expanding health insurance coverage for various segments of society, including the homeless. Although homeless people who lack health insurance face strong financial barriers to health services, providing them with health insurance may not appreciably increase their demand for health care if they also face important non-financial barriers. We investigate the relationship between insurance and utilization for this group based on estimates from an empirical model of medical care use and insurance coverage. Using our estimates, we simulate potential effects of policy changes on various types of utilization, including use of mental health services and treatment for alcohol or other drug abuse.

Monocyte chemotactic protein 4 (MCP-4), a novel structural and functional analogue of MCP-3 and eotaxin

A novel human CC chemokine complementary DNA was identified in a library constructed from human fetal RNA, cloned into a baculovirus vector, and expressed in Sf9 insect cells. The mature recombinant protein that was released had the NH2-terminal sequence pyro-QPDALNVPSTC...and consisted of 75 amino acids. Minor amounts of two variants of 77 and 82 residues (NH2 termini: LAQPDA...and FNPQGLAQPDA...) were released as well. The novel chemokine was designated monocyte chemotactic protein 4 (MCP-4) and the variants were designated (LA)MCP-4 and (FNPQGLA)MCP-4. MCP-4 shares the pyroglutamic acidproline NH2-terminal motif and 56-61% sequence identity with the three known monocyte chemotactic proteins and is 60% identical to eotaxin. It has marked functional similarities to MCP-3 and eotaxin. Like MCP-3, MCP-4 is a chemoattractant of high efficacy for monocytes and T lymphocytes. On these cells, it binds to receptors that recognize MCP-1, MCP-3, and RANTES. On eosinophils, MCP-4 has similar efficacy and potency as MCP-3, RANTES, and cotaxin. It shares receptors with eotaxin and shows full cross-desensitization with this cosinophil-selective chemokine. Of the two variants, only (LA)MCP-4 could be purified in sufficient quantities for testing and was found to be at least 30-fold less potent than MCP-4 itself. This suggests that the 75-residue form with the characteristic NH2 terminus of an MCP is the biologically relevant species.

Cytokines and growth factors signal through tyrosine phosphorylation of a family of related transcription factors

The ability of cytokines to activate distinct but overlapping sets of genes defines their characteristic biological response. We now show that IFN gamma, IL-3, IL-4, IL-6, erythropoietin, EGF, and CSF-1 activate differing members of a family of latent cytoplasmic transcription factors. Although these factors have distinct physical and functional properties and exhibit different patterns of expression, they share many important features, including recognition of a related set of enhancer elements, rapid activation, tyrosine phosphorylation, and cross-reactivity to antibodies against p91, a cytoplasmic signaling protein activated by IFN alpha, IFN gamma, and IL-6. These shared features point to either parallel or common patterns of signal transduction. A general model of cytokine signal transduction is presented, in which receptor-associated tyrosine kinases activate ligand-specific members of a family of signal-transducing factors. Once activated, these factors carry their signals to the nucleus, where they bind a family of related enhancer elements.

Market work, wages, and men's health

In this paper, we investigate the complex interrelations among work-time, wages, and health identified in the Grossman model of the demand for health. Hansen's generalized method of moments techniques are employed to estimate a 3-equation simultaneous model designed to capture the time dependent character of these interrelationships. We then estimate simpler models with more restrictive assumptions commonly found in the literature and find substantial differences between these estimates and those from our simultaneous model. For example, the positive relationship between work-time and health found in other studies disappears when the relevant simultaneities are taken into account.

Signaling by the cytokine receptor superfamily: JAKs and STATs

A variety of cytokines, lymphokines and growth factors function by interacting with receptors that are members of the cytokine receptor superfamily. These receptors share extracellular motifs and have limited similarity in their cytoplasmic domains. Although lacking catalytic domains, this family of receptors couples ligand binding with the induction of tyrosine phosphorylation. Recent studies have shown that this is mediated by members of the Janus kinase (JAK) family of cytoplasmic protein tyrosine kinases. JAKs physically associate with the membrane-proximal region of the ligand-bound receptor, leading to their tyrosine phosphorylation and activation. The activated JAKs phosphorylate the receptors as well as cytoplasmic proteins belonging to a family of transcription factors called the signal transducers and activators of transcription (STATs), providing a novel signaling pathway that is shared by all members of the cytokine receptor superfamily.

v-myb blocks granulocyte colony-stimulating factor-induced myeloid cell differentiation but not proliferation

To understand the effects of v-myb expression on mammalian hematopoietic cell differentiation, we have constructed a retroviral vector which can efficiently express v-myb gene product in mammalian cells. Infection of interleukin-3-dependent murine progenitor cell line 32D Cl3, which undergoes terminal differentiation to mature granulocytes in the presence of granulocyte colony-stimulating factor (GCSF), with this recombinant retrovirus does not abrogate its requirement of interleukin-3 for growth. However, expression of v-myb in these cells blocks their ability to differentiate in response to GCSF. Instead, the v-myb-infected cells proliferate indefinitely in the presence of GCSF. 32D Cl3 cells infected with empty vector carrying only the neomycin resistance gene responded to the addition of GCSF in a manner identical to that of the uninfected cells and underwent terminal differentiation into granulocytes. These results suggest that oncogenic forms of myb gene bring about transformation by blocking the differentiation signal derived by cytokines while promoting the proliferative signal transduction pathways.

Axons induce differentiation of neurofibroma Schwann-like cells

Neurofibromatosis type 1 (NF-1, von Recklinghausen's disease) is characterized by the focal accumulation of Schwann-like cells (SLC) to form subcutaneous and plexiform neurofibromas and schwannomas. The aim of the present study was to determine whether NF-SLC are competent to differentiate in the presence of axons. Five dermal neurofibromas from five patients with NF-type 1 were enzymatically dissociated and the resultant cells were co-cultured with fetal rat dorsal root ganglion neurons. The cultures were studied by indirect immunofluorescence microscopy using antibodies against galactocerebroside (galC), P0 glycoprotein, human nerve growth factor receptor (NGFR) and human myelin-associated glycoprotein (MAG). SLC were strongly NGFR+ but galC- and MAG-SLC for the 2 weeks of coculture. After 3 weeks in vitro, SLC-NGFR was down-regulated but some of the spindle shaped cells had become galC+. MAG-SLC first appeared after 5 weeks in vitro but P0 glycoprotein was never detected when studied up to 6 weeks. Our data demonstrate that axons induce SLC to down-regulate surface NGFR and to express some myelin components in a qualitatively normal fashion.

Human central nervous system primitive neuroectodermal tumor expressing nerve growth factor receptors: CHP707m

A primitive neuroectodermal tumor (PNET) presented as a cerebral hemispheric mass in a 33-year-old man. Bone marrow metastases were discovered 11 months later. A cell line (CHP707m) was derived from these metastases. In culture, the cells showed features of neuronal differentiation, forming short neurites and synthesizing low-molecular-weight neurofilament protein. Northern blotting showed the tumor cells express nerve growth factor (NGF) receptor messenger RNA, and fluorescence-activated cell-sorting demonstrated NGF receptors on the cell surface. Western blotting showed CHP707m NGF receptors are truncated. The receptors are functional; they bind iodine 125-labeled mouse NGF with an affinity of 1.6 x 10(-9) M, and short-term treatment with NGF induces expression by the tumor cells of the proto-oncogene, c-fos. Although CHP707m is the first central nervous system PNET cell line proven to express NGF receptors, immunohistological survey of tissue sections prepared from human central nervous system PNETs showed that 13 of 35 contained NGF receptor-positive tumor cells. Thus, more than one-third of such tumors might be responsive to the effects of NGF.

Regulation of Schwann cell nerve growth factor receptor by cyclic adenosine 3',5'-monophosphate

Previous studies indicated that Schwann cells in immature nerves express nerve growth factor (NGF) receptors, and that this expression is down regulated during development but re-induced by Wallerian degeneration. It was also shown that immature Schwann cells are induced to express galactocerebroside and other molecules characteristic of mature Schwann cells by either contact with an axon or treatment with the cyclic adenosine 3',5'-monophosphate (cAMP) analogues dibutyryl cAMP (dbcAMP) and 8-bromo cAMP or the adenylate cyclase activator forskolin. In the present study, NGF receptors on the surface of cultured Schwann cells were demonstrated by binding of an anti-rat NGF receptor monoclonal antibody or of radioiodinated NGF. Treatment of cultured Schwann cells with cAMP analogues or forskolin resulted in a progressive decrease in both immunoreactive NGF receptors and radioiodinated NGF binding. The cultured Schwann cells contained a polyadenylated RNA species homologous with human melanoma NGF receptor mRNA in sequence and size. The amount of this NGF mRNA was lower in cAMP analogue-treated than in untreated Schwann cells.

Regulation of myelin P0 glycoprotein synthesis in cultured rat Schwann cells and continuous rat PNS cell lines

We studied the effects of agents that raise intracellular cyclic AMP on synthesis of myelin components by cultured neonatal rat sciatic nerve Schwann cells and by continuous PNS cell lines derived from the fusion of neonatal rat sciatic nerve Schwann cells with rat RN22 Schwannoma. Treatment with N6,2'-O-dibutyryl cyclic AMP (dibutyryl cyclic AMP) caused a fourfold increase in Schwann cell incorporation of 35SO4 into sulfogalactosylceramide (sulfatide), and elicited a 10- to 20-fold increase in such incorporation by the continuous PNS cell lines; a similar effect on PNS cell line sulfatide radiolabelling was obtained with forskolin. Cultured Schwann cells expressed barely detectable levels of myelin P0 glycoprotein (P0) mRNA and myelin basic protein (MBP) mRNA. Treatment of the Schwann cells with axolemmal fragments or with dibutyryl cyclic AMP did not elicit a detectable increase in the levels of these mRNAs. The PNS cell lines constitutively expressed much higher levels of P0 mRNA than did the Schwann cells, and synthesized immunochemically demonstrable P0 glycoprotein, but did not express MBP. Treatment of the PNS cell lines with dibutyryl cyclic AMP markedly reduced expression of P0 mRNA and also diminished immunoreactive P0 glycoprotein. These PNS cell lines should prove useful for further studies of the control of Schwann cell differentiation.

Cultured rat Schwann cells express low affinity receptors for nerve growth factor

Schwann cell cultures prepared from postnatal Sprague-Dawley rat sciatic nerves were used to demonstrate the presence of specific receptors for the beta-subunit of nerve growth factor (NGF) on rat Schwann cells. Indirect immunofluorescence microscopy with a monoclonal antineuronal NGF receptor (NGFR) antibody indicated that NGFR antigen was expressed on the surface of Schwann cells but not of endoneurial fibroblasts. Studies with 125I-NGF confirmed this distribution of NGFR in the cultures and showed that the Schwann cell NGFR had a single NGF binding affinity (Kd of 1.8 x 10(-9) M). 125I-NGF binding by the cultured Schwann cells increased with time in vitro, reaching a plateau level on the 4th day, but decreased with increasing age, reaching 40% of the neonatal value in Schwann cells isolated from 12-day-old rats. Treatment of the cultures with NGF did not alter Schwann cell phenotype, survival or proliferation.

Schwann-like cells cultured from human dermal neurofibromas. Immunohistological identification and response to Schwann cell mitogens

Primary cultures prepared from dermal and plexiform neurofibromas contain Schwann-like cells and fibroblast-like cells. SLC are elongated and bipolar or multipolar. By indirect immunofluorescence light microscopy, living SLC bind antibodies against laminin and against nerve growth factor receptor to their surface, but not antibodies against fibronectin. In these respects, cultured SLC are indistinguishable from cultured human adult Schwann cells. FLC are flat and pleomorphic. By indirect immunofluorescence light microscopy, living FLC bind antibodies against fibronectin but not against laminin or NGFR. In these respects, cultured FLC are indistinguishable from cultured human adult endoneurial fibroblasts. Considerable purification of viable SLC from SLC/FLC mixed cultures can be achieved by flow cytofluorometry using a monoclonal anti-NGFR antibody. Tritiated thymidine radioautography indicated that mitosis of SLC in mixed SLC/FLC cultures prepared from dermal neurofibromas is infrequent in MEM with 10% calf serum, more frequent in RPMI 1640 medium with 15% fetal calf serum. Central nervous system axolemmal fragments (rat or human) elicited a greater than 10-fold SLC proliferative response in mixed SLC/FLC cultures from three of seven dermal neurofibromas (from six patients with neurofibromatosis), but had no effect on SLC mitosis in cultures from the other four dermal neurofibromas. SLC mitosis was inhibited by concentrations of cyclic adenosine 3',5'-monophosphate analogues known to stimulate proliferation of normal rat Schwann cells. Glial growth factor partially purified from bovine pituitaries stimulated SLC mitosis both in SLC/FLC mixed cultures and in cultures of purified SLC. The studies we have described indicate that neurofibroma SLC can be cultured, unequivocally identified in culture by morphological and immunohistological criteria, purified, and stimulated to proliferate by several Schwann cell mitogens. Further quantitative comparisons of the baseline and mitogen-stimulated rates of proliferation of SLC and age-matched control human Schwann cells are needed, however, to determine which of the two alternate pathogenetic mechanisms for formation of neurofibromas mentioned in the introduction is correct.

Expression of melanoma-associated antigens by normal and neurofibroma Schwann cells

The cell surface antigen distribution on traumatic neuroma Schwann cells and neurofibroma Schwann-like cells was characterized using monoclonal antibodies that define melanoma-associated antigens. Immunofluorescence staining of cultured cells, immunoprecipitation of radioiodinated antigens from cells placed in short-term cultures, and immunoperoxidase staining of frozen tissue sections revealed most of the melanoma-associated antigens tested on traumatic neuroma and neurofibroma Schwann cells and on fetal and adult femoral nerve. The cross-reactivity of the antibodies with neural cells may reflect the common neural crest embryological origin of Schwann cells and melanocytes. Cell sorter analysis of neurofibroma cells using a monoclonal antibody directed against the melanoma nerve growth factor receptor resulted in cell cultures highly enriched for Schwann-like cells which may bear the genetic defect responsible for neurofibromatosis. The antigen detected by this monoclonal antibody is the neurofibroma nerve growth factor receptor and the antibody was a potent inhibitor of nerve growth factor binding to neurofibroma cells.

Tissue culture studies of Schwann cell proliferation and differentiation

Neonatal rat sciatic nerve Schwann cells in monolayer culture are stimulated to proliferate and to express a lipid and a protein characteristic of myelin by agents which raise intracellular cyclic adenosine 3',5'-monophosphate. Both glial growth factor and axolemmal fragments increase the rate of mitosis of cultured rat and human Schwann cells. Rat Schwann cell mitosis is enhanced by a soluble factor produced by concanavalin A-stimulated blood mononuclear cells and inhibited by lead salts. Schwann-like cells cultured from human dermal and plexiform neurofibromas resemble normal human Schwann cells in phenotype and response to mitogens.

Specific and potent mitogenic effect of axolemmal fraction on Schwann cells from rat sciatic nerves in serum-containing and defined media

Using cultures of Schwann cells from neonatal rat sciatic nerves, we examined the mitogenic activity of an axolemmal fraction from adult rat CNS. Axolemmal fraction proved a potent mitogen, stimulating [3H]thymidine incorporation into Schwann cell DNA 13.5-fold over control values when axolemmal fraction equivalent to 16 micrograms of protein per culture microwell or more was added. Half maximal stimulation was obtained with addition of axolemmal fraction equivalent to 4 micrograms of protein. The concentration-dependence and magnitude of the mitogenic response of the cultured cells were nearly identical whether they were maintained in vitro for 1 day or for 2 weeks prior to addition of the axolemmal fraction. A study of the time-course of the effect of axolemmal fraction on Schwann cell mitosis showed that maximal [3H]thymidine incorporation took place during the fifth day after addition of axolemmal fraction. Axolemmal fraction also produced stimulation of [3H]thymidine incorporation into Schwann cells, seeded and cultured in a serum-free defined medium. Though the concentration-dependence of the mitogenic effect in the absence of serum was similar to that in a serum-containing medium, maximal stimulation in the defined medium was only 2.8-fold. The mitogenic activity of axolemmal fraction was rapidly and almost totally inactivated by sonication or homogenization, and was partially lost after exposure to heat. The mitogenic activities of plasma membrane fragments from rat skeletal muscle or rat erythrocytes, and of mitochondrial fragments (the major contaminant of the axolemmal fraction) were one-tenth that of axolemmal fraction or less. In contrast to glial growth factor prepared from bovine pituitaries (GGF-BP), which stimulates proliferation of both fibroblasts and Schwann cells, axolemmal fraction induced proliferation of Schwann cells but not of endoneurial fibroblasts; cultures treated with axolemmal fraction demonstrated a 3-fold increase in Schwann cell population in 10 days without detectable increase in number of fibroblasts. Also in contrast to GGF-BP, the mitogenic effect of which is considerably enhanced by simultaneous addition of cholera toxin to the medium, cholera toxin had no effect on the Schwann cell proliferative response to axolemmal fraction.