Effect of daclizumab on TReg counts and EGFRvIII-specific immune responses in GBM

2034

Background: TRegs are increased in patients with GBM and constitutively express the high affinity interleukin-2 receptor (IL-2Rα). Treatment with an antibody that blocks IL-2Rα signaling functionally inactivates and eliminates TRegs without inducing autoimmune toxicity in murine models. We hypothesized that daclizumab, a commercially-available, IL-2Rα-specific antibody would function identically.Methods: A randomized phase II clinical trial assessed the effects of daclizumab in the context of the cancer vaccine, CDX-110, which is comprised of an EGFRvIII-specific peptide sequence linked to KLH. EGFRvIII is a constitutively activated and immunogenic mutation not expressed in normal tissues, but widely expressed in GBMs and other neoplasms. In patients with newly-diagnosed, EGFRvIII+ GBM, after resection and radiation/TMZ, patients received CDX-110 vaccinations biweekly x 3, then monthly until tumor progression in combination with TMZ (200 mg/m2 x 5/28 days). Half the patients were randomized to receive daclizumab (1mg/Kg x1) at the first vaccine. The others received saline in a double-blinded fashion.Results: There were no drug related SAEs. EGFRvIII-specific immune responses were generated in all patients, and all immune responses were sustained or enhanced during subsequent TMZ cycles. Preliminary analysis (n = 4) suggests that daclizumab reduces Treg (CD4+CD25+CD45RO+FOXP3+) numbers [change 82.4 ± 7.1% from baseline (p = 0.011; t-test)] without reducing overall CD8+ or CD4+ T-cell counts. Tregs decreased only 3.7 + 11.0% after vaccination in the saline treated group during the same interval. Preliminary analysis (n = 4) also suggest that daclizumab enhanced EGFRvIII-specific immune responses (p = 0.01; t-test) and enhanced the titer of cytotoxic EGFRvIII-specific IgG1 isotype antibodies compared to the saline treated group (p = 0.003; t-test) and compared to previously vaccinated patients who did not receive daclizumab (p = 0.0015; t-test). TTP and OS survival in both arms has not been reached. Conclusions: Daclizumab may reduce Treg counts in patients with GBM. TMZ and daclizumab may enhance EGFRvIII-targeted immune responses despite lymphodepletion. These combinations are currently under further investigation.

[Table: see text]

Epidermal growth factor receptor variant III (EGFRvIII) vaccine (CDX-110) in GBM

2021

Background: Unlike conventional therapies for GBM, immunologic targeting of tumor-specific gene mutations allows precise eradication of neoplastic cells with reduced toxicity. EGFRvIII is a constitutively activated and immunogenic mutation not expressed in normal tissues, but widely expressed in GBM and other neoplasms. The cancer vaccine CDX-110 is comprised of an EGFRvIII-specific peptide sequence linked to keyhole limpet hemocyanin (KLH). Methods: A phase II multi-center trial assessed the immunogenicity and efficacy of CDX-110 in patients with newly-diagnosed, EGFRvIII+ GBM. After resection and radiation / TMZ, patients received CDX-110 vaccinations biweekly x 3, then monthly until tumor progression. Sequential cohorts received CDX-110 alone [ACTIVATE (n = 18)] or in combination with TMZ (200 mg/m2 x 5/28 days [ACT II A (n = 13)]) or (100 mg/m2 x 21/28 days [ACT II B (n=10)]). Results: Reversible systemic drug hypersensitivity reactions were seen in 1 ACTIVATE and 4 ACT II patients. Two patients had non-specific changes on MRI which were possibly due to the vaccine but which resolved. Despite grade 2 or 3 lymphopenia in all ACT II patients, EGFRvIII-specific immune responses were generated in all patients, and all immune responses were sustained or enhanced during subsequent TMZ cycles. Although ACT II B patients had more severe TMZ-induced lymphopenia, they developed greater EGFRvIII-specific immune responses (p = 0.028) when compared to ACT II A. EGFRvIII-specific IgG1 also increased in avidity with vaccination (Ka>>2x109M-1) in a randomly selected subset of 4 patients (p = 0.000068). Of the 23 recurrent tumors studied, 18 lost EGFRvIII expression (p = 0.001). There are no significant differences between ACT II A and B in estimated median TTP (18.5 vs. 14.9 months, p = 0.31) and OS (23.6 vs. 19.9 months, p = 0.75). ACTIVATE TTP (14.2 months) and OS (26.0 months) and ACT II TTP (15.2 months) and OS (23.6 months) compare favorably to a TMZ-treated, matched historical control group (TTP: 6.3 months; OS: 15.0 months). Conclusions: CDX-110 vaccination in patients with GBM appears very promising. TMZ enhances immune responses despite lymphodepletion. CDX-110 with simultaneous TMZ is under further investigation in a larger phase II trial.

[Table: see text]

Temozolomide as a vaccine adjuvant in GBM

2020

Background: Cytotoxic chemotherapy that induces lymphopenia is predicted to ablate the benefits of active antitumor immunization. Temozolomide (TMZ) is an effective chemotherapeutic for patients with glioblastoma multiforme (GBM), but it induces significant lymphopenia. Methods: In a Phase II trial, patients with newly-diagnosed, completely resected GBM are vaccinated with an EGFRvIII-specific peptide q2 weeks X 3 after radiation (XRT)(∼60Gy) and TMZ (75mg/m2/d) and then monthly with 5 day TMZ cycles (200mg/m2/d). Results: TMZ induces transient, Grade 3 lymphopenia (< 500 cells/uL) in 70% of patients after the first TMZ cycle with nadirs occurring 14–21 days after treatment (n=10). Regulatory T cell (TReg) (CD4+CD25++CD45RO+FOXP3+) levels increased from 5.2+1.5% (3.3 - 7.5) to 11.8+2.6% (6.9 - 13.8)(P=0.0004; paired t-test) with TMZ and XRT and averaged 12.2+4.0% (6.4 - 18.1) after the second TMZ cycle (P=0.007) (n=6). Despite these findings, in patients assayed, both humoral and cellular EGFRvIII-specific immune responses appear to be enhanced with TMZ. Median survival and TTP after vaccination is 26.2 weeks with no patients progressing (n=8). Conclusions: Despite conventional dogma, we demonstrated that both chemotherapy and immunotherapy can be delivered concurrently without negating the effects of immunotherapy. TMZ-induced lymphopenia may prove to be synergistic with a peptide vaccine.

No significant financial relationships to disclose.

Maximization of signal derived from cDNA microarrays

Microarray technology is a powerful tool for generating expression data on a large number of genes simultaneously. However, as for any assay, it must be reproducible to give confidence in the results. Using a classical statistical method--the factorial design of experiments--we have assessed the effects of different experimental factors in our system. Significant effects on signal were seen when the standard components were substituted with a different enzyme, fluorescent label, or RNA purification method. This has led to the implementation of an improved procedure that maximizes signal without affecting the variability of the system, thus increasing the signal-to-noise ratio. In addition, we were able to quantify the variability between microarrays and replicates within microarrays.

Temozolomide delivered by intracerebral microinfusion is safe and efficacious against malignant gliomas in rats

Intracerebral microinfusion (ICM) is an innovative technique of delivering therapeutic agents throughout large portions of the brain that circumvents the blood-brain barrier, minimizes systemic toxicity, and provides a homogeneous distribution of the infused agent. Temozolomide is a novel methylating agent with proven efficacy against malignant gliomas (MGs) after systemic administration but with dose-limiting myelotoxicity. Because MGs rarely metastasize, systemic drug delivery is unnecessary. Therefore, we evaluated the efficacy and toxicity of ICM with temozolomide in an athymic rat model of human MGs. Treatment of rats by ICM with temozolomide 3 days after intracerebral challenge with D54 human MG xenograft increased median survival by 128% compared with rats treated by ICM with saline, by 113% compared with rats treated with i.p. saline, and by 100% compared with rats treated with i.p. temozolomide (P < 0.001). Delay of treatment until 9 days after tumor challenge still resulted in a 23% increase in median survival in rats treated by ICM of temozolomide compared with rats treated with i.p. temozolomide. In addition, overall, 21.7% of rats treated by ICM with temozolomide survived for > 100 days without clinical or histological evidence of tumor. The dose of temozolomide delivered by ICM in this study was limited only by drug solubility, and no neurological or systemic toxicity could be attributed to ICM with temozolomide. Therefore, ICM of temozolomide may offer significant advantages in the treatment of MGs.

Unarmed, tumor-specific monoclonal antibody effectively treats brain tumors

The epidermal growth factor receptor (EGFR) is often amplified and rearranged structurally in tumors of the brain, breast, lung, and ovary. The most common mutation, EGFRvIII, is characterized by an in-frame deletion of 801 base pairs, resulting in the generation of a novel tumor-specific epitope at the fusion junction. A murine homologue of the human EGFRvIII mutation was created, and an IgG2a murine mAb, Y10, was generated that recognizes the human and murine equivalents of this tumor-specific antigen. In vitro, Y10 was found to inhibit DNA synthesis and cellular proliferation and to induce autonomous, complement-mediated, and antibody-dependent cell-mediated cytotoxicity. Systemic treatment with i.p. Y10 of s.c. B16 melanomas transfected to express stably the murine EGFRvIII led to long-term survival in all mice treated (n = 20; P < 0.001). Similar therapy with i.p. Y10 failed to increase median survival of mice with EGFRvIII-expressing B16 melanomas in the brain; however, treatment with a single intratumoral injection of Y10 increased median survival by an average 286%, with 26% long-term survivors (n = 117; P < 0.001). The mechanism of action of Y10 in vivo was shown to be independent of complement, granulocytes, natural killer cells, and T lymphocytes through in vivo complement and cell subset depletions. Treatment with Y10 in Fc receptor knockout mice demonstrated the mechanism of Y10 to be Fc receptor-dependent. These data indicate that an unarmed, tumor-specific mAb may be an effective immunotherapy against human tumors and potentially other pathologic processes in the "immunologically privileged" central nervous system.

Intrathecal busulfan treatment of human neoplastic meningitis in athymic nude rats

The current study was designed to evaluate the toxicity and activity of Spartaject Busulfan, a microcrystalline preparation of busulfan, following its intrathecal administration into a nude rat model of human neoplastic meningitis. Animals were treated through permanent indwelling subarachnoid catheters. Human glioma D-456 MG growing in the subarachnoid space was treated with 8.1 micromol of intrathecal Spartaject Busulfan. Single-dose therapy was also subsequently compared with 4 doses of 8.1 and 2.0 micromol busulfan, respectively, against D-456 MG neoplastic meningitis. Additional experiments evaluated a saline control versus 8.1 micromol x 1, 6.2 micromol x 4 and 4.1 micromol x 4, respectively, against D-456 MG. A single dose of 8.1 micromol of intrathecal Spartaject Busulfan resulted in an increase in median survival of 61.7% compared with the saline control. In experiment 2, all busulfan treatments showed increases in median survival of 142.8% (8.1 micromol x 1), 52.3% (2.0 micromol x 4), and 23% (8.1 micromol x 4) (p < 0.001 for all groups) compared with the saline control. These results suggest that a narrow therapeutic dose range for both toxicity and activity has been defined for intrathecal busulfan in the treatment of human neoplastic meningitis in athymic nude rats. Although busulfan has only limited activity against solid tumors, the high doses achievable in the CSF following intrathecal administration coupled with the steep dose-response relationships of alkylating agents, provide rationale for further evaluation of this agent.

Bone marrow-derived dendritic cells pulsed with tumor homogenate induce immunity against syngeneic intracerebral glioma

To evaluate the efficacy and toxicity of dendritic cell (DC) based therapy for intracerebral gliomas, we utilized a cell line derived from an astrocytoma that arose spontaneously in a VM/Dk mouse. This astrocytoma mirrors human gliomas phenotypically, morphologically and secretes transforming growth factor (TGF)-betas, immunosuppressive cytokines secreted by human gliomas. Systemic vaccination of mice with DCs pulsed with tumor homogenate followed by intracranial tumor challenge produced a > 160% increase in median survival (p = 0.016) compared with mice vaccinated with PBS or unpulsed DCs (p = 0.083). Fifty percent of mice treated with pulsed DCs survived long-term. Immunologic memory was demonstrated by survival of mice rechallenged with tumor. Both cell-mediated and humoral immunity was induced. On histological examination only focal areas of demyelination at the tumor implantation site were present. There was no evidence that autoimmune encephalomyelitis was induced by DC vaccination. Therefore, in a murine model, vaccination with DCs pulsed with glioma tumor homogenate is a safe and effective therapy against a syngeneic glioma located in the immunologically privileged central nervous system (CNS).

Radiotoxicity of systemically administered 211At-labeled human/mouse chimeric monoclonal antibody: a long-term survival study with histologic analysis

PURPOSE

The antitenascin human/mouse chimeric monoclonal antibody labeled with the alpha-particle-emitting radionuclide 211At is of interest as an endoradiotherapeutic agent for the treatment of brain tumors. To facilitate the investigation of 211At-labeled chimeric 81C6 in patients, the long-term radiotoxicity of this radiopharmaceutical has been evaluated.

METHODS AND MATERIALS

Antibody labeling was performed using N-succinimidyl 3-[211At]astato-benzoate. After an initial dose-finding experiment, a second toxicity study was carried out at 4 dose levels in groups of 30 nonthyroid blocked B6C3F1 mice per group (15 males, 15 females). Male mice received either saline or 15-81 kBq/g and females received either saline or 16-83 kBq/g of 211At-labeled antibody. Ten animals (5 males, 5 females) were followed for 6 months and the remainder for 1 year.

RESULTS

The lethal dose in 10% of animals (LD10) for 211At-labeled chimeric 81C6 was 46 kBq/g in females and 102 kBq/g in males. Toxic effects--perivascular fibrosis of the intraventricular septum of the heart, bone marrow suppression, splenic white pulp atrophy, and spermatic maturational delay--generally were confined to a few animals receiving the highest doses of labeled antibody.

CONCLUSIONS

The LD10 of 211At-labeled chimeric 81C6 in this mouse strain was about half that of [211At]astatide. These results establish the preclinical maximum tolerated dose of 211At-labeled chimeric 81C6 and define in the mouse the target organs for toxicity. These studies will be useful for determining starting doses for clinical studies with 211At-labeled chimeric 81C6.

Regional treatment of epidermal growth factor receptor vIII-expressing neoplastic meningitis with a single-chain immunotoxin, MR-1

The incidence of neoplastic meningitis is on the rise. Neoplastic meningitis can result from a direct seeding of the neuraxis by primary brain tumors or by hematogeneous spread of systemic solid tumors. A frequent genetic alteration in primary brain tumors such as gliomas is an in-frame deletion in the epidermal growth factor receptor (EGFR) gene EGFRvIII, which brings together what were normally distant polypeptide sequences in the intact receptor. A novel glycine is formed at the fusion junction, resulting in a unique and tumor-specific target. By using phage display, we have isolated a single-chain antibody specific for the EGFRvIII mutation and expressed it with a modified form of the Pseudomonas exotoxin to form the immunotoxin MR1scFvPE38KDEL (MR-1). The multiple dose toxicity and therapeutic efficacy of MR-1 immunotoxin were tested in an athymic rat model of neoplastic meningitis. The maximally tolerated doses in non-tumor-bearing rats were three doses of 3 microg each. For therapeutic studies, the target was a neoplastic meningitis induced by intrathecal inoculation of the EGFRvIII-expressing human glioma U87MG.deltaEGFR. A dose escalation study compared the survival of three equal doses of 1, 2, and 3 microg of MR-1 immunotoxin with saline or 3 microg of the control immunotoxin specific for the interleukin 2 receptor, anti-Tac. All animals treated with three doses of saline or 3 microg of anti-Tac died, with median survival of 7 and 10 days, respectively. There were 75% (six of eight) long-term survivors in the group treated with three doses of 1 microg and 57% (four of seven) long-term survivors in the groups treated with three doses of either 2 or 3 microg of MR-1 immunotoxin. None of the MR-1 immunotoxin-treated groups reached median survival by the termination of the study at 53 days. Therefore, median survival was estimated to be >53 days, resulting in an estimated increase in median survival of >657% compared with saline and 430% versus anti-Tac. Compartmental therapy with three doses of 2 microg of MR-1 immunotoxin is effective in the treatment of EGFRvIII-expressing neoplastic meningitis. This dose was found to have no clinical or histopathological effects on non-tumor-bearing animals. MR-1 immunotoxin is, therefore, considered specific and safe within its therapeutic window. Phase I clinical trials for tumors invading the intrathecal space that express the EGFRvIII target should be initiated.

Treatment of neoplastic meningitis with intrathecal temozolomide

Neoplastic meningitis (NM) results from leptomeningeal dissemination of cancers arising within the central nervous system or metastasizing to the leptomeninges from systemic neoplasms. The inability to produce therapeutic drug levels intrathecally (i.t.) with systemic administration and the minimal efficacy of chemotherapeutic agents currently available for direct i.t. use limit therapy. Temozolomide [8-carbamoyl-3-methylimidazo[5,1-d]-1,2,3,5-tetrazin-4([3H])-one] is a novel methylating agent with proven activity against intraparenchymal malignant gliomas (MGs). Insolubility of the standard formulation prevents its efficacious use as an i.t. agent, however. To overcome this obstacle, we have developed a unique microcrystalline formulation of temozolomide with greatly enhanced solubility. Treatment of athymic rats bearing subarachnoid MER- human MG xenografts with four doses of i.t. microcrystalline temozolomide over a 2-week period produced a 142% increase in median survival at individual doses of 2.2 micromol (P = 0.0073) and a >367% increase in median survival at individual doses of 6.8 micromol (P = 0.0015). At the higher dose tested, three of eight rats treated developed no neurological symptoms and had no evidence of residual tumor on histological examination after treatment. Use of this microcrystalline formulation in athymic rats bearing subarachnoid MER+ human MG xenografts increased median survival >132% (P < 0.0058) at both dose levels tested. Toxicity directly attributable to the i.t. administration of microcrystalline temozolomide was exhibited in the highest dose groups only and was limited to small patchy areas of focal demyelination involving <5% of spinal cord long tracks.

Analysis of gene mutations and clastogenicity following short-term treatment with azathioprine in MutaMouse

The mutagenicity and clastogenicity of the immunosuppressive drug azathioprine (AZA), a multitissue rodent carcinogen and IARC-classified human carcinogen, was investigated using transgenic lacZ mice (MutaMouse). Male animals (n = 5 per group) were dosed with AZA (10, 50, 100 mg/kg p.o. daily for 5 days), vehicle (n = 10), or the positive control, chlorambucil (15 mg/kg i.p., n = 3), and killed 24 hr or 25 days after the last treatment. Micronucleus assays were performed with bone marrow (24-hr samples) or peripheral blood (24-hr and 25-day samples) and DNA was extracted from bone marrow and liver for gene mutation analysis at the transgenic lacZ locus. AZA induced 5.3-111.3-fold increases in %MNPCE (P < 0.01) in bone marrow compared with vehicle control, accompanied by 4.4-5. 6-fold increases in %MNRETs (P < 0.01) in peripheral blood. Chlorambucil caused a 14.5-fold increase in %MNRET and there was evidence of significant stem cell toxicity in both positive control and AZA treatment groups. By day 25, however, there was evidence of substantial recovery of the bone marrow as determined by the frequency of RET, and the %MNRET in all treatment groups was the same as the vehicle control. Analysis of lacZ MF showed 1.4-1.6-fold increases in AZA 24-hr bone marrow samples, increasing to approximately 2.0-fold above concurrent controls by day 25 (medium dose P < 0.05, high dose P < 0.01). For liver, there was a 2-fold increase in MF (P < 0.05) in the 24-hr sample at the highest dose only, and increases of 1.3-1.5-fold by day 25 in the medium (P < 0. 05) and high (P = 0.055) dose groups, respectively. The positive control, chlorambucil, induced 2-3-fold increases (P < 0.01) in mean MF in both bone marrow (25-day sample) and liver (24-hr and 25-day samples). These data confirm the clastogenicity of AZA in the mouse, and show that this compound induces gene mutations in bone marrow and liver, in vivo, at the highest dose and supports the view that AZA is a genotoxic carcinogen.

Local production of TGF beta1 inhibits cerebral edema, enhances TNF-alpha induced apoptosis and improves survival in a murine glioma model

We have previously reported that local secretion of either TNF-alpha or TGF beta1 by intracerebral SMA-560 malignant glioma tumor cells can reduce or eliminate tumor growth in mice. However, the use of TNF-alpha, while improving the overall survival of tumor bearing animals, was associated with early toxic deaths due to cerebral edema. In the present study, we demonstrate that TNF-alpha induces apoptosis of the SMA 560 cell line, as does TGF beta1, and that these two cytokines act in an additive fashion to enhance apoptosis and thus, to inhibit SMA 560 cell growth in vitro. Next, we show that the production of TGF beta1 when added to TNF-alpha production by central nervous system tumors in vivo abrogates any early deaths seen due to TNF-alpha toxicity and leads to a larger percentage of animals surviving CNS tumor challenge. Finally, we demonstrate that the production of TGF beta1 by tumor cells is associated with the abolition of tumor-associated cerebral edema in both TNF-alpha and in non-TNF-alpha producing tumors. These results are important for the development of effective and less toxic therapies for brain tumors, as well as for examining the pathogenesis of tumor-related cerebral edema.

The class III variant of the epidermal growth factor receptor (EGFRvIII): characterization and utilization as an immunotherapeutic target

Any immunotherapeutic approach to cancer cell eradication is based upon the specific recognition of neoplastic cells and the sparing of surrounding normal tissue; perhaps nowhere is this distinction more important than within the central nervous system, due to the diffuse infiltrative nature of primary glial tumor cell growth. Whether ultimate effect moieties are immunoglobulins, fragments and/or their constructs with drugs, toxins, radionuclides, or immune cells, the specificity of effector: cell surface marker is crucial. This review describes the identification, immunologic characterization, and biologic behavior of a transmembrane tumor-specific altered growth factor receptor molecule which may well serve as a mediator of multiple immunotherapeutic approaches: the class III variant of the epidermal growth factor receptor, EGFRvIII.

Characterization of a spontaneous murine astrocytoma and abrogation of its tumorigenicity by cytokine secretion

OBJECTIVE

The promise of immunotherapies developed against brain tumors in animal models has not been realized in human clinical trials. This may be because of the routine use of rodent tumors artificially induced by chemicals or viruses that do not accurately portray the intrinsic qualities of spontaneously arising human tumors and that often fail to incorporate the role of immunosuppressants, such as transforming growth factor-beta, that are secreted by human gliomas. From an astrocytoma that arose spontaneously in inbred VM/Dk mice, we have characterized a highly tumorigenic spontaneous murine astrocytoma cell line (SMA-560) that retains features of glial differentiation and naturally produces high levels of biologically active transforming growth factor-beta. We have used this model to determine whether cytokine production by tumor cells will inhibit intracerebral astrocytoma growth.

METHODS

Packaging cell lines producing replication-incompetent retroviral vectors were used to transfect the SMA-560 cell line in vitro with the genes encoding the murine cytokines interleukin (IL)-2, IL-3, IL-4, IL-6, tumor necrosis factor-alpha, gamma-interferon, or granulocyte-macrophage colony-stimulating factor or the costimulatory molecule B7.1 (CD80).

RESULTS

Mice challenged intracerebrally with 5000 untransfected SMA-560 cells all succumbed to tumor within 30 days, with a median survival of 25 days. In contrast, mice challenged with SMA-560 cells producing IL-2, IL-4, or tumor necrosis factor-alpha each had a more than 400% increase in median survival (P < 0.0001). In these groups, 78.3% (18 of 23 mice), 66.7% (10 of 15 mice), and 60% (6 of 10 mice) of the mice, respectively, remained alive without evidence of tumor for longer than 100 days after the initial tumor challenge. All other cytokines tested and the expression of B7.1 failed to result in an increase in median survival.

CONCLUSION

Using a spontaneous astrocytoma model in an inbred mouse strain, we have shown that cytokine production by glial tumors can abrogate their tumorigenicity in vivo despite production of transforming growth factor-beta. These results predict that approaches directed at cytokine production within intracerebral astrocytomas may be efficacious in human trials and that the "immunological privilege" of the brain may not be absolute under such conditions.

A genetically modified allogeneic cellular vaccine generates MHC class I-restricted cytotoxic responses against tumor-associated antigens and protects against CNS tumors in vivo

An active immunotherapeutic strategy using transfected allogeneic cells for targeting the mutant epidermal growth factor receptor (EGFRvIII) on intracranial tumors was examined. Immunization with allogeneic 300.19/EGFRvIII cells induced CD8+ cytotoxic T-lymphocytes against EGFRvIII bearing syngeneic B16-F10 melanoma or 560 astrocytoma cells (H-2b), but not against allogeneic NR6 cells (H-2q) also bearing EGFRvIII significant NK cell activity was also noted in vitro. Vaccination protected against intracranial challenge with EGFRvIII-positive tumor, with 50% long term survival. In vivo depletions of effector cell subsets demonstrated the requirements for both CD8+ and CD4+ T-cells but not NK cells in producing this protective effect. These data demonstrate the generation of significant, antigen-specific and MHC class I-restricted cytotoxic immune responses which are effective against tumors present in the CNS.

Improved targeting of an anti-epidermal growth factor receptor variant III monoclonal antibody in tumor xenografts after labeling using N-succinimidyl 5-iodo-3-pyridinecarboxylate

Monoclonal antibody (mAb) L8A4, specific for the tumor-associated mutant epidermal growth factor receptor variant III (EGFRvII), is internalized and degraded after cell binding. Four paired-label experiments were performed in athymic mice bearing EGFRvIII-positive xenografts to determine the suitability of N-succinimidyl 3-iodo-5-pyridinecarboxylate (SIPC) for labeling this internalizing mAb. In mice with HC2 20 d2 xenografts, tumor uptake reached a maximum of 32.7 +/- 2.0% injected dose/g when labeled using SIPC, a value significantly higher (P < 0.05, paired t test) than that observed when L8A4 was labeled using lodogen (24.4 +/- 2.2% injected dose/g). The specificity of mAb uptake in HC2 20 d2 and U87MG(delta)EGFR xenografts was measured in separate experiments by coadministration of L8A4 and nonspecific, isotype-matched P3X63Ag8 mAb, both radioiodinated using SIPC. Tumor localization indices were approximately 10 or more by 72 h, a degree of specificity 3-4 times higher than that reported previously when labeling was performed using the tyramine cellobiose (TCB) method. In a final study directly comparing L8A4 labeled using SIPC and TCB, similar tumor levels were obtained (SIPC, 33.7 +/- 6.1% injected dose/g at 24 h; TCB, 37.8 +/- 6.7% injected dose/g at 24 h); however, tumor-to-tissue ratios for the liver, spleen, and kidneys were 3 times higher with SIPC at later time points. These results suggest that SIPC is a promising method for labeling this anti-EGFRvIII mAb and possibly other mAbs that internalize after binding.

Intraarterial O6-benzylguanine enables the specific therapy of nitrosourea-resistant intracranial human glioma xenografts in athymic rats with 1,3-bis(2-chloroethyl)-1-nitrosourea

The prognosis for patients with malignant gliomas continues to be dismal. The high degree of resistance of gliomas to nitrosourea-based chemotherapy is one major factor in poor treatment outcome. The identification of O6-alkylguanine-DNA alkyltransferase (AGAT) as a major determinant of nitrosourea resistance has resulted in the development of several agents to inactivate this repair protein and counteract tumor cell resistance. However, a major problem in preclinical trials has been the marked nitrosourea dose limitations imposed by the prior administration of AGAT-depleting agents. We investigated the AGAT depletion and selective enhancement of BCNU activity of intraarterial (i.a.) O6-benzylguanine (O6BG) in the human malignant glioma xenograft D-456 MG growing intracranially (i.e.) in athymic rats. Whereas i.a. O6BG at 2.5 mg/kg produced 100% inhibition of D-456 MG AGAT i.e. activity 8 h after administration, intraperitoneal (i.p.) O6BG at this dose produced only 40% inhibition, requiring dose escalation to 10 mg/kg to produce 100% AGAT depletion. Prior administration of i.p. O6BG (10 mg/kg) and i.a. O6BG (2.5 mg/kg) limited maximum tolerated intravenous (i.v.) BCNU doses (37.5 mg/kg when given alone) to 6.25 and 25 mg/kg, respectively. Higher doses of BCNU alone or in combination with O6BG produced histopathologic evidence of cerebral and hepatic toxicity. Therapy experiments revealed a significantly improved median survival for rats treated with O6BG i.a. (2.5 mg/kg) plus BCNU i.v. (25 mg/kg, days 61 and 59 in duplicate experiments) compared with saline (day 21. P = 0.001). O6BG i.a. or i.p. (days 22 and 23, P = 0.001), BCNU i.v. (37.5 mg/kg, day 29, P = 0.001), and O6BG i.p. (10 mg/kg), plus BCNU i.v. (6.25 mg/kg, day 37, P < 0.001). Therefore, O6BG i.a., by virtue of rapid AGAT depletion and selective uptake into i.c. tumors, offers significant potential for regional chemomodulation of AGAT-mediated nitrosourea resistance in malignant human gliomas with concomitant reduction of systemic toxicity.

Subcutaneous vaccination with irradiated, cytokine-producing tumor cells stimulates CD8+ cell-mediated immunity against tumors located in the "immunologically privileged" central nervous system

Vaccination with cytokine-producing tumor cells generates potent immune responses against tumors outside the central nervous system (CNS). The CNS, however, is a barrier to allograft and xenograft rejection, and established tumors within the CNS have failed to respond to other forms of systemic immunotherapy. To determine what barriers the "immunologically privileged" CNS would pose to cytokine-assisted tumor vaccines and what cytokines would be most efficacious against tumors within the CNS, we irradiated B16 murine melanoma cells producing murine interleukin 2 (IL-2), IL-3, IL-4, IL-6, gamma-interferon, or granulocyte-macrophage colony stimulating factor (GM-CSF) and used these cells as subcutaneous vaccines against tumors within the brain. Under conditions where untransfected B16 cells had no effect, cells producing IL-3, IL-6, or GM-CSF increased the survival of mice challenged with viable B16 cells in the brain. Vaccination with B16 cells producing IL-4 or gamma-interferon had no effect, and vaccination with B16 cells producing IL-2 decreased survival time. GM-CSF-producing vaccines were also able to increase survival in mice with pre-established tumors. The response elicited by GM-CSF-producing vaccines was found to be specific to tumor type and to be abrogated by depletion of CD8+ cells. Unlike the immunity generated against subcutaneous tumors by GM-CSF, however, the effector responses generated against tumors in the CNS were not dependent on CD4+ cells. These data suggest that cytokine-producing tumor cells are very potent stimulators of immunity against tumors within the CNS, but effector responses in the CNS may be different from those obtained against subcutaneous tumors.

Chimeric anti-tenascin antibody 81C6: increased tumor localization compared with its murine parent

When labeled using the Iodogen method, a chimeric antibody composed of the human IgG2 constant region and the variable regions of murine anti-tenascin 81C6 exhibited superior uptake in human glioma xenografts compared with its murine parent. In the current study, three paired-label experiments were performed in athymic mice with subcutaneous D-54 MG human glioma xenografts to evaluate further the properties of radioiodinated chimeric 81C6. These studies demonstrated that (a) the enhanced tumor uptake of chimeric 81C6 is specific; (b) when labeling was performed using N-succinimidyl 3-iodobenzoate, chimeric 81C6 again showed preferential accumulation in tumor compared with murine 81C6; and (c) the tumor uptake advantage observed previously with murine 81C6 for N-succinimidyl 3-iodobenzoate compared with Iodogen labeling did not occur with chimeric 81C6.

Radiotoxicity of systematically administered [211At]astatide in B6C3F1 and BALB/c (nu/nu) mice: a long-term survival study with histologic analysis

PURPOSE

The present study undertook to establish the dose (LD) of systematically administered (via tail vein) sodium [211At]astatide that would kill 10% (LD10) of exposed animals in two mouse models and to evaluate the resulting histologic lesions.

METHODS AND MATERIALS

Three dose escalation experiments were carried out using groups of 10 3- to 4-week-old, 20 +/- 2 g B6C3F1 mice, and one dose escalation experiment was carried out with groups of 10 4- to 6-week-old, 22 +/- 2 g BALB/c (nu/nu) mice. All animals were weighed daily and checked twice daily for general health; autopsies were performed within 12 h of death.

RESULTS

The LD10 (95% confidence interval) level of free [211At]astatide at 360 days was 15.1 microCi (5.2-19.1 microCi) in B6C3F1 mice and was associated with a 37.8% weight difference from saline controls (p < 0.001). In the BALB/c (nu/nu) mice, the LD10 at 360 days was 7.7 microCi (0-14.2 microCi), while a dose of 10 microCi (0.42 microCi g(-1)) was associated with a 9.44% weight difference vs. saline controls (p < 0.05). Exclusive of the well-known effects on thyroid, [211At]astatide activity levels were associated with severe bone marrow depression, testicular atrophy, focal alopecia, and nuclear atypia of the epidermoid mucosa of the fore-stomach in the B6C3F1 mice; at activity levels approximating LD10 at 360 days, mild changes in the heart, liver, stomach, and spleen were observed. For BALB/c (nu/nu) mice, administration of 10 microCi was associated at autopsy with mild histologic lesions in the heart, stomach, liver, and spleen.

CONCLUSIONS

These studies provide a basis for the design of further investigations of [211At]-labeled compounds as therapeutic agents.

Efficacy of compartmental administration of immunotoxin LMB-1 (B3-LysPE38) in a rat model of carcinomatous meningitis

LMB-1 (B3-LysPE38) is an immunotoxin composed of the tumor-reactive monoclonal antibody B3 and a genetically engineered form of Pseudomonas exotoxin. Monoclonal antibody B3 reacts with a carbohydrate epitope that is found on a number of solid tumors (e.g., breast, ovarian, and lung carcinomas) that frequently invade the intrathecal space, causing neoplastic meningitis. The Pseudomonas exotoxin has been engineered to remove the binding domain to eliminate nonspecific binding. A model of human neoplastic meningitis using rats bearing the human epidermoid carcinoma A431 was used for therapeutic studies of immunotoxin LMB-1. Therapy was initiated 3 days after injection of the tumor cells, which was one third of the median survival time of untreated rats. A single intrathecal injection of 40 microgram increased median survival from 9 days with saline injection to 16 days (78%, P < 0.001), and a single dose of 200 microgram increased median survival to 25 days (188%, P < 0. 001). Three doses of 40 or 200 microgram given on days 3, 6, and 8 significantly increased the median survival of 9.5 days associated with saline injection to 40.5 days (326% increase) and 33.0 days (247% increase), respectively, with two long-term survivors (191-day survival) in each treatment group. LMB-1 had no therapeutic effect on the treatment of two B3 antigen-negative neoplastic meningitis models. Treatment of the antigen-positive A431 neoplastic meningitis with B3 alone or a nonspecific monoclonal, MOPC, coupled to the engineered Pseudomonas exotoxin produced no survival effects. Nontumor-bearing athymic rats showed no toxicity with a single dose of either 40 microgram or 200 microgram, or 3 doses of 40 microgram. However, when they were given three doses of 200 microgram, these rats showed weight loss and loss of neurological function, and two of eight animals died. These studies indicate that, in the range of the most therapeutically effective dosage, the immunotoxin LMB-1 is tolerated in the intrathecal space and should be considered for human intrathecal trials.

Tumor-specific anti-epidermal growth factor receptor variant III monoclonal antibodies: use of the tyramine-cellobiose radioiodination method enhances cellular retention and uptake in tumor xenografts

Amplification and rearrangement of the epidermal growth factor receptor (EGFR) gene are characteristics of many types of tumors. One class of EGFR mutations, EGFRvIII, is characterized by an in-frame deletion resulting in a truncated external domain of the receptor. EGFRvIII was first identified in a subset of gliomas and has since been found in some non-small cell lung carcinomas and breast carcinomas. mAbs specific for this variant form of EGFR but unreactive with the wild-type EGFR have been reported from our laboratory. This study further characterizes three of these antibodies. We determined, via radiolabeling techniques and immunofluorescence microscopy, that, after cell binding in vitro, the anti-EGFRvIII-specific mAbs internalize at 37 degrees C. Furthermore, subsequent to internalization, the antibodies were processed intracellularly, presumably by lysosomal degradation. We also examined the use of an alternative radiolabeling procedure that uses nonmetabolizable radio-iodinated tyramine cellobiose. Our results show that the tyramine cellobiose labeling method allows for greater tumor cell retention of radiolabel in vitro (76% for tyramine cellobiose and 27% for Iodo-Gen after 24 h). Paired-label biodistribution studies in athymic mice indicate that anti-EGFRvIII mAb L8A4 localizes specifically to EGFRvIII-expressing tumor xenografts with a maximum of 34.3 +/- 7.6% injected dose/g when labeled using tyramine cellobiose compared with a maximum of 14.9 +/- 4.3% injected dose/g using Iodo-Gen; similar results were obtained with mAb H10. These results suggest that the anti-EGFRvIII mAbs may serve as potential carriers for radioconjugate- and immunotoxin-based therapies for tumors expressing EGFRvIII.

Intraarterial administration of melphalan for treatment of intracranial human glioma xenografts in athymic rats

Malignant gliomas will affect 15,000-17,000 Americans each year and carry a dismal prognosis. Adjuvant chemotherapy is hampered by inadequate drug delivery, systemic toxicity, and a markedly variable biological sensitivity. Intraarterial (i.a.) therapy may enhance selectivity by improving tumor drug delivery and reducing systemic toxicity. Using melphalan given i.a., we studied the therapy of intracranial human glioma xenografts in male athymic nude rats (mean weight, 300 g) which were inoculated intracerebrally with D-54 MG and D-456 MG. On Days 6 and 7 (D-54 MG) or Days 9 and 10 (D-456 MG), rats randomized by body weight and treated with single-dose melphalan given i.a. at 0.5 or 0.75 mg produced significantly higher median survival (D-54 MG, Days 33 and 32; D-456 MG, Days 52 and 54, respectively) compared with i.a. saline (D-54 MG, Day 14, P < 0.001; D-456 MG, Day 24, P = 0.000) or melphalan given i.v. at 0.75 mg and 0.9 mg (D-54 MG only; Day 19, P < 0.001; Day 23, P < 0.001, respectively) and at 0.5 and 0.75 mg (D-456 MG only; Day 26 for both doses, P = 0.00). Although a dose-dependent increase in median survival (D-54 MG, 0.25 mg, Day 18; 0.5 mg, Day 28.5; 0.75 mg, Day 32.5) was observed with i.a. administered melphalan, no significant difference was apparent between 0.5 and 0.75 mg in either tumor model (D-54 MG, P = 0.15; D-456 MG, P = 0.37). Toxicity studies in nontumor-bearing athymic rats yielded a maximum tolerated dose of 0.8 mg for i.a. administered melphalan. This dosage was superior in spite of different xenograft permeabilities (apparent mean blood-to-tissue transport [K] values for alpha-aminoisobutyric acid, 5.8 for D-54 MG and 1.3 for D-456 MG). Pharmacokinetic experiments demonstrated a significant first pass advantage for i.a. (versus i.v.) melphalan. The short plasma half-life, marked antiglioma activity, and lack of requirement for metabolic activation indicate that i.a. melphalan holds considerable promise for human glioma therapy.

Intrathecal administration of single-chain immunotoxin, LMB-7 [B3(Fv)-PE38], produces cures of carcinomatous meningitis in a rat model

LMB-7 [B3(Fv)-PE38] is a single-chain immunotoxin constructed from the murine monoclonal antibody B3 and a truncated from of Pseudomonas exotoxin PE38. Antibody B3 recognizes a carbohydrate epitope found on solid tumors that frequently invade the intrathecal space and cause neoplastic meningitis. We tested the therapeutic value of intrathecally administered LMB-7 by using a model of human neoplastic meningitis in athymic rats. This model is representative of a clinical situation in that antibody B3 cross-reacts with a number of normal tissues that can be used to monitor potential systemic toxicity. Treatment was begun 3 days after A431 tumor implantation. Without treatment, the animals median survival was 10 days. Intrathecal administration of 10 micrograms of LMB-7 in 40 microliters on days 3, 5, and 7 produced 4 of 10 and 8 of 10 long-term survivors (> 170 days) in two experiments. Of the long-term survivors, 2 of 4 and 7 of 8 survivors had no microscopic evidence of tumor and were considered histologic cures. Lack of significant toxicity in the effective dose range and specificity make LMB-7 an excellent candidate for intrathecal treatment of neoplastic meningitis in humans.

Radioimmunotherapy of neoplastic meningitis in rats using an alpha-particle-emitting immunoconjugate

Because of their short range and high linear energy transfer, alpha-particles may be particularly effective in the treatment of neoplastic meningitis. Monoclonal antibody 81C6 was labeled with alpha-particle-emitting 211At using N-succinimidyl3-[211At]astatobenzoate, and the efficacy and toxicity of this immunoconjugate were evaluated in an athymic rat model. Animals were given injections via a chronic indwelling catheter with 5 x 10(5) TE-671 human rhabdomyosarcoma cells and treated 8 days later with single intrathecal doses of either saline or 4-18 microCi of 211At-labeled specific 81C6 antibody or isotype-matched control 211At-labeled 45.6 antibody. In the first experiment, 4, 7, and 13 microCi 211At-labeled 81C6 produced statistically significant (P = 0.004-0.02) increases in median survival of 33, 29, and 51%, respectively, as compared with saline. Two of 10 animals receiving the 13-microCi dose lived for 6 months before being killed for histological analysis. In the second experiment, 12 microCi of 211At-labeled 45.6 did not increase median survival significantly relative to saline control, while 12 microCi of 211At-labeled 81C6 increased median survival by 113% (P < 0.005) and resulted in 33% apparent cures. Five of 10 animals receiving 18 microCi of 211At-labeled 81C6 survived until they were killed at 295 days. An additional study was performed in animals given intrathecal injections of 5 x 10(6) TE-671 cells and given a single dose of 18 microCi of 211At-labeled 81C6 or 211At-labeled 45.6. At this higher cell number, significantly prolonged survival was still seen for specific antibody as compared with saline (P < 0.001) and control antibody (P < 0.05). These results suggest that treatment with 211At-labeled monoclonal antibodies may be a valuable approach for neoplastic meningitis.

Intrathecal melphalan therapy of human neoplastic meningitis in athymic nude rats

We report the activity and toxicity of intrathecal melphalan in the treatment of human neoplastic meningitis in the subarachnoid space of athymic nude rats. Animals received injections via chronic indwelling subarachnoid catheters with 5 x 10(5) or 5 x 10(6) TE-671 human rhabdomyosarcoma cells or 5 x 10(6) D-54 MG human glioma cells and were treated with melphalan on days 8, 5, or 5, respectively. Melphalan toxicity in nontumor-bearing rats was assessed at single doses of a 2.0, 3.0, 4.0, or 5.0 mM solution, with clinical and histological evidence of neurotoxicity observed at the 4.0 and 5.0 mM levels. Multiple-dose toxicity studies using a dosing schedule of twice a week for two weeks with a 0.25, 0.5, 0.75, 1.0, 1.5, or 2 mM solution revealed dose-dependent clinical and histological evidence for toxicity at all dosages. Treatment of TE-671 with a single dose of 2.0 mM intrathecal melphalan produced an increase in median survival of 442% compared with saline controls (P < 0.003). Comparison of a single dose of 1.0 or 2.0 mM melphalan with a multiple dose regimen at 0.25 or 0.5 mM melphalan in the treatment of TE-671 revealed increases in median survival of 50% for 1.0 mM, 57% for 2.0 mM, 79% for 0.5 mM, and 111% for 0.25 mM concentrations. Comparison of a single dose of 1 mM melphalan with multiple doses of 0.25 mM melphalan in the treatment of D-54 MG revealed an increase in median survival of 475+% for each of the regimens. Intrathecal melphalan may be an important new addition in the treatment of neoplastic meningitis and is currently being evaluated clinically in a Phase 1 trial.

PET imaging of osteosarcoma in dogs using a fluorine-18-labeled monoclonal antibody Fab fragment

Four dogs with histologically confirmed osteogenic sarcoma were studied with PET following intravenous injection of the 18F-labeled Fab fragment of TP-3, a monoclonal antibody specific for human and canine osteosarcomas.

METHODS

The antibody fragment was labeled using the N-succinimidyl 8-[(4'-[18F]fluorobenzyl)amino]suberate acylation agent. Blood clearance of activity was biphasic in all dogs but half-times were variable (T1/2 beta = 2-13 hr). Catabolism of labeled Fab was reflected by the decrease in protein-associated activity in serum from more than 90% at 1 min to 60%-80% at 4 hr.

RESULTS

PET images demonstrated increased accumulation of 18F at the primary tumor site relative to normal contralateral bone in one dog as early as 15 min after injection. Biopsies obtained after euthanasia indicated higher uptake at the edges of the tumor as observed on the PET scans. Tumor uptake was 1-3 x 10(-3)% injected dose/g, a level similar to that reported for other Fab fragments in human tumors. In the three dogs with metastatic disease, early PET images reflected activity in the blood pool but later uptake was observed in suspected metastatic sites.

CONCLUSIONS

These results, although preliminary, suggest that PET imaging of 18F-labeled antibody fragments is feasible and that dogs with spontaneous tumors could be a valuable model for preclinical research with radioimmunoconjugates.

Generation and characterization of a mouse/human chimeric antibody directed against extracellular matrix protein tenascin

The murine anti-tenascin monoclonal antibody 81C6, following iodination, has been shown to be an efficient localizing and therapeutic agent in both subcutaneous and intracranial human glioma xenograft models in athymic mice and rats. Similarly, effective monoclonal antibody 81C6 localization has been demonstrated in glioma patients, and Phase I trials with the intact murine IgG2b kappa molecule are currently in progress. In order to maximize the potential for repeated administration by minimizing murine Fc-mediated immunogenicity and reducing Fc-mediated immune effects, we created murine 81C6 variable region/human IgG2 chimeric monoclonal antibodies by the molecular cloning of the variable region genes of mouse 81C6 and their genetic linkage to human constant region exons. The resulting chimeric constructs were introduced into SP2/0 cells, and stable transfectomas were selected by G418 and mycophenolic acid resistance. The resistant clones were screened for anti-tenascin activity on tenascin-coated plates by enzyme-linked immunosorbent assay. The N-terminal amino acid sequence of both heavy and light chains of the purified chimeric 81C6 antibody matched exactly with that of the native mouse 81C6 as well as with that deduced from the nucleotide sequence. The production level of chimeric 81C6 (13.9 mg/ml) from ascites in the highest expressing transfectoma was much higher than that of native mouse 81C6 (2.5 mg/ml). The chimeric antibody showed the same specificity and equivalent affinity for human intact tenascin or tenascin-expressing cells as the native mouse 81C6 antibody. Direct comparison of radioiodinated chimeric and radioiodinated mouse 81C6 biodistribution in subcutaneous and intracranial xenograft-bearing mice showed higher tumor-to-normal tissue ratios for chimeric 81C6 as compared with native mouse 81C6. The improved localizing and clearance characteristics of chimeric 81C6 in xenograft model systems suggests that chimeric 81C6 would be an improved reagent for intracompartmental therapy of tenascin-expressing tumors in the human central nervous system.

Investigation of a synthetic peptide as immunogen for a variant epidermal growth factor receptor associated with gliomas

We have previously demonstrated antibody production to a glioma-associated variant form of the human epidermal growth factor receptor in rabbits that had received a synthetic peptide mimicking the unique primary structure of the variant protein as immunogen. We report here the response of mice, rabbits, goats, and macaques immunized by various protocols to this peptide. Titers to both peptide- and cell-elaborated variant receptor were measured, and the capacity to recognize the variant receptor in human tumor samples was determined. Within the range of species and strains investigated, we demonstrated a variable species-associated response to the peptide (rabbits > mice > goats > rats > macaques). Rabbits and a single goat produced specific, high titer antibody activity to the variant receptor protein following immunization with peptide alone. Murine titers to the parent protein were not appreciable following peptide immunization alone; additional immunization with variant receptor as expressed on cell membranes was used to boost this response.

Intraarterial therapy of human glioma xenografts in athymic rats using 4-hydroperoxycyclophosphamide

The addition of chemotherapy, notably using nitrosoureas, in the treatment of patients with glioblastoma multiforme has resulted in only modest improvements in long-term patient survival over the use of surgical intervention and irradiation alone. Intraarterial (i.a.) chemotherapy offers the potential benefit of increasing tumor drug delivery because of first-pass drug uptake, while minimizing systemic drug levels and toxicity. We have now investigated the i.a. therapy of intracerebral human glioma xenografts in athymic rats with 4-hydroperoxycyclophosphamide (4-HC), a preactivated derivative of cyclophosphamide. Athymic male rats were given intracerebral injections of the human glioma line D-54 MG. On Day 5 after injection, the rats were randomized (n = 8-10) by body weight (mean weight, approximately 300 g). In one set of experiments, each group received either i.v. saline, i.a. saline, 6 mg i.a. 4-HC, 6 mg i.v. 4-HC (6 mg), or 12 mg i.v. 4-HC. Intraarterial 4-HC produced significant increases in median survival (Day 24) compared with i.a. saline controls (140% increase), equivalent doses given i.v. (71% increase), and twice the equivalent dose given i.v. (50% increase) (by Wilcoxon rank sum analysis, P < 0.05 is statistically significant). The i.a. maximum tolerated dose was subsequently determined to be approximately 12.5 mg in non-tumor-bearing rats. Further experiments demonstrated a dose-response increase in survival for i.a. dosages of 6, 9, and 12.5 mg with significant improvement when compared with saline controls and 12.5 mg i.v. Pharmacokinetic experiments also demonstrated a significant first-pass uptake advantage for i.a. (versus i.v.) administered 4-HC. The short plasma half-life and marked antiglioma activity of 4-HC, without the need for hepatic activation, suggest a therapeutic application of this drug in the i.a. treatment of brain tumors.

Deletion-mutant epidermal growth factor receptor in human gliomas: effects of type II mutation on receptor function

Malignant human glioma D-298 MG amplifies a rearranged epidermal growth factor receptor (EGFR) gene (c-erbB proto-oncogene), resulting in an in-frame deletion of 83 amino acids in domain IV of the extracellular domain of the EGFR. EGF and transforming growth factor-a (TGF-a) bound to the mutant EGFR with high affinity and enhanced the intrinsic mutant EGFR kinase activity. The mutant EGFR was capable of transducing EGF-stimulated glioma cell proliferation and invasiveness in an in vitro three-dimensional spheroid model. The deletion-mutant EGFR in D-298 MG is capable of being activated by growth factor; this suggests that overexpression of this mutant EGFR protein rather than structural alteration may be the more significant biologic event.

Anti-synthetic peptide antibody reacting at the fusion junction of deletion-mutant epidermal growth factor receptors in human glioblastoma

We have investigated human gliomas that amplify and rearrange the epidermal growth factor receptor gene, with generation of an in-frame deletion mutation of 802 nucleotides in the external domain. This in-frame deletion mutation generates a local amino acid sequence at the fusion junction of what normally were distant polypeptide sequences in the intact epidermal growth factor receptor. This 14-amino acid peptide was chemically synthesized, coupled to keyhole limpet hemocyanin, and used as an immunogen in rabbits. The elicited antibody reacted specifically with the fusion peptide in ELISA. The anti-fusion junction peptide antibody was purified by passage of the antiserum over a peptide affinity column with acidic elution. The purified antibody selectively bound the glioma deletion mutant as compared to the intact epidermal growth factor receptor as assessed by immunocytochemistry, immunofluorescence, immunoprecipitation with gel electrophoresis, and binding experiments using radioiodinated antibody. These data indicate that it is feasible to generate site-specific anti-peptide antibodies that are highly selective for mutant proteins in human tumors. The anti-peptide antibody described here, and other mutation site-specific antibodies, should be ideal candidates for tumor immunoimaging and immunotherapy.

Activity of intrathecal 4-hydroperoxycyclophosphamide in a nude rat model of human neoplastic meningitis

Neoplastic meningitis can result from leptomeningeal dissemination of a variety of cancers. We now report the development of animal models of human neoplastic meningitis and activity of intrathecal 4-hydroperoxycyclophosphamide (4-HC) against the human rhabdomyosarcoma cell line TE-671 and the human glioma cell line D-54 MG grown in the subarachnoid space of athymic rats. The injection of 5 x 10(5) TE-671 or D-54 MG cells resulted in leptomeningeal tumor growth from the base of the brain to the cauda equina. Daily weights and neurological examinations revealed progressive neurological deficits and weight loss, with death occurring between Days 21 and 27 for TE-671 and Days 14 and 26 for D-54 MG. 4-HC toxicity in non-tumor-bearing rats was assessed at dose levels of 2.0, 10.0, 15.0, and 20.0 mM, with clinical and histological evidence of neurotoxicity observed at the 2 highest dose levels. Intrathecal treatment with 4-HC on Day 8 following injection of TE-671 resulted in an increase in median survival of 20% (P = 0.04) at 1.0 mM 4-HC and 41% (P less than 0.001) at 2.5 mM 4-HC. Intrathecal treatment with 4-HC (2.5 mM) on Day 5 following injection of D-54 MG resulted in an increase in median survival of 23% (P = 0.009). These studies show the usefulness of the athymic rat model of human neoplastic meningitis and demonstrate the efficacy in vivo of intrathecally administered 4-HC against a human glioma and a human rhabdomyosarcoma cell line and the lack of toxicity at therapeutic levels of 4-HC in normal athymic rats.

Radioimmunotherapy of intracerebral human glioma xenografts with 131I-labeled F(ab')2 fragments of monoclonal antibody Mel-14

The administration of radiolabeled monoclonal antibodies to improve the treatment of malignant gliomas is dependent upon achieving effective tumor radiation dose while sparing normal tissues. We have evaluated the efficacy of 131I-labeled F(ab')2 fragment of monoclonal antibody Mel-14, an IgG2a reactive with the chondroitin sulfate proteoglycan antigen of gliomas, melanomas, and other neoplasms, in prolonging survival of athymic mice transplanted intracerebrally with D-54 MG human glioma xenografts. Studies indicated that in vitro immunoreactivity, affinity, and tumor localization in vivo of radiolabeled Mel-14 F(ab')2 were maintained at specific activities of 10-13 microCi/micrograms. Intravenous injection of 1500 microCi/115 micrograms or 2000 microCi/154 micrograms 131I-labeled Mel-14 F(ab')2 into mice 6-7 days after xenograft implantation resulted in significant survival prolongation over control animals (P = 0.009 using Wilcoxon rank sum analysis). In another experiment, 1500 microCi/126 micrograms 131I-labeled Mel-14 F(ab')2 improved survival significantly over controls (P = 0.006), while 1500 microCi/220 micrograms 131I-labeled nonspecific antibody did not (P = 0.2). Increasing the injected radiation dose to 3000 microCi 131I-labeled Mel-14 F(ab')2 did not significantly increase survival in tumor-bearing mice, because of supervening radiation toxicity. However, giving 3000 microCi 131I-labeled Mel-14 F(ab')2 in two doses of 1500 microCi, 48 h apart, did significantly prolong animal survival over controls (P = 0.001). Estimated radiation dose to tumor was 915 rad after injection of 3000 microCi 131I-labeled Mel-14 F(ab')2 in two doses, a dose higher than that delivered to normal tissues. The results of this study suggest that radiolabeled Mel-14 F(ab')2 be evaluated as an agent for radioimmunotherapy trials.

Synthesis of radioiodinated N-succinimidyl iodobenzoate: optimization for use in antibody labelling

N-succinimidyl-3-(tri-n-butylstannyl)benzoate (m-BuATE), N-succinimidyl-3-(tri-methylstannyl)benzoate (m-MeATE) and N-succinimidyl-4-(tri-n-butylstannyl)benzoate (p-BuATE) were synthesized and radioiodinated using either N-chlorosuccinimide (NCS) or t-butylhydroperoxide (TBHP) as the oxidant. Radiohalogenation of m-MeATE proceeded more rapidly than m-BuATE. NCS was the more efficient oxidant at reaction times less than 15 min; use of both TBHP and NCS resulted in nearly quantitative yields after 15 min when m-MeATE was used. Using NCS, achieving optimal antibody coupling and specific binding required purification of the active ester by HPLC; in contrast, with TBHP, only Sep-Pak purification was needed.

Acute abdomen caused by placenta percreta in the second trimester

A woman with a history of "in utero" diethylstilbestrol exposure but no prior uterine surgery presented with an acute abdomen at 21 weeks' gestation. She had hemoperitoneum associated with placenta percreta.

Immunocytochemical binding to neurons of serum from spinocerebellar degeneration patients

Antineural antibodies have been described in sera of patients with neurodegenerative disorders. We looked for the presence of those antibodies in the sera of patients with spinocerebellar degeneration. Serum IgG from four patients with familial spinocerebellar degeneration showed strong binding to cerebral cortical neurons, Purkinje cells, and dorsal root ganglia of normal human tissue sections stained with the peroxidase antiperoxidase (PAP) method at serum dilution of 1:500. No binding to neuroglia cells or cells of the granular layer of the cerebellum was seen. Sera from four immediate, asymptomatic relatives (son or sibling) showed only moderate binding to Purkinje cells and to dorsal root ganglia, but not to cortical neurons. Sera from seven patients with neurological diseases other than spinocerebellar degeneration and from five healthy subjects showed no binding to neural elements. The findings may be of value in the diagnosis and screening of patients suspected of having spinocerebellar degeneration; however, the significance of these antineural antibodies in the pathogenesis of spinocerebellar degeneration is uncertain and awaits further studies.