Vemurafenib in patients with BRAFV600 mutation-positive metastatic melanoma: final overall survival results of the randomized BRIM-3 study

Background

The BRIM-3 trial showed improved progression-free survival (PFS) and overall survival (OS) for vemurafenib compared with dacarbazine in treatment-naive patients with BRAFV600 mutation-positive metastatic melanoma. We present final OS data from BRIM-3.

Patients and methods

Patients were randomly assigned in a 1 : 1 ratio to receive vemurafenib (960 mg twice daily) or dacarbazine (1000 mg/m2 every 3 weeks). OS and PFS were co-primary end points. OS was assessed in the intention-to-treat population, with and without censoring of data for dacarbazine patients who crossed over to vemurafenib.

Results

Between 4 January 2010 and 16 December 2010, a total of 675 patients were randomized to vemurafenib (n = 337) or dacarbazine (n = 338, of whom 84 crossed over to vemurafenib). At the time of database lock (14 August 2015), median OS, censored at crossover, was significantly longer for vemurafenib than for dacarbazine {13.6 months [95% confidence interval (CI) 12.0-15.4] versus 9.7 months [95% CI 7.9-12.8; hazard ratio (HR) 0.81 [95% CI 0.67-0.98]; P = 0.03}, as was median OS without censoring at crossover [13.6 months (95% CI 12.0-15.4) versus 10.3 months (95% CI 9.1-12.8); HR 0.81 (95% CI 0.68-0.96); P = 0.01]. Kaplan-Meier estimates of OS rates for vemurafenib versus dacarbazine were 56% versus 46%, 30% versus 24%, 21% versus 19% and 17% versus 16% at 1, 2, 3 and 4 years, respectively. Overall, 173 of the 338 patients (51%) in the dacarbazine arm and 175 of the 337 (52%) of those in the vemurafenib arm received subsequent anticancer therapies, most commonly ipilimumab. Safety data were consistent with the primary analysis.

Conclusions

Vemurafenib continues to be associated with improved median OS in the BRIM-3 trial after extended follow-up. OS curves converged after ≈3 years, likely as a result of crossover from dacarbazine to vemurafenib and receipt of subsequent anticancer therapies.

ClinicalTrials.gov

NCT01006980.

Histology and outcomes of newly detected lung lesions in melanoma patients

BACKGROUND

Melanoma frequently metastasizes to the lung. Improved radiologic techniques may decrease the need for biopsy of such lesions. The aim of this study was to examine factors predictive of a positive biopsy of melanoma.

METHODS

Using the Memorial Sloan-Kettering Cancer Center melanoma database, all patients with melanoma who had undergone biopsy of a suspicious new lung lesion from 1996 to 2009 were identified. Age, date of diagnosis, histology, and stage were obtained. Chart review was carried out to obtain medical history, smoking status, radiological appearance, and histology of lung lesions biopsied.

RESULTS

Two hundred and twenty-nine patients were identified; median age was 63 years; 48% were never smokers; 27% had a prior nonmelanoma cancer; 88% of lung nodules were malignant: 69% melanoma, 19% other cancers. Among 113 patients undergoing positron emission tomography (PET), proportions of benign, melanoma, and nonmelanoma 2-[fluorine-18]fluoro-2-deoxy-D-glucose-avid nodules did not differ (P = 0.53). On multivariable analysis, >stage I melanoma, negative smoking history, multiple lung nodules, and no prior nonmelanoma cancer were significantly associated with a melanoma biopsy result rather than other cancer.

CONCLUSIONS

In this study, 31% of lung lesions were not melanoma. In the subset undergoing PET, this did not differentiate between benign and malignant lesions. Biopsy is mandated in melanoma patients with new lung nodules.

Phase III randomized, open-label, multicenter trial (BRIM3) comparing BRAF inhibitor vemurafenib with dacarbazine (DTIC) in patients with V600EBRAF-mutated melanoma

LBA4

Background: About 50% of melanomas have an activating V600EBRAF mutation which led to the hypothesis that inhibition of the mutated BRAF kinase may be of clinical benefit. Phase I and II trials with vemurafenib (previously PLX4032/RO5185426), an orally available inhibitor of oncogenic BRAF kinase, showed response rates (RR; CR+PR) >50% in V600EBRAF- mutated melanoma patients (pts). We conducted a phase III trial to determine if vemurafenib improved overall survival (OS) and progression-free survival (PFS) in melanoma pts with V600EBRAF mutation. Methods: Pts with previously untreated, unresectable stage IIIC or stage IV melanoma that tested positive for V600EBRAF mutation by the cobas 4800 BRAF V600 Mutation Test were randomized (1:1) to vemurafenib (960 mg po bid) or DTIC (1,000 mg/m2, IV, q3w). Randomization was stratified by PS, stage, LDH, and geographic region. Pts were assessed for tumor responses after weeks 6, 12, and then q9 weeks. Co-primary endpoints were OS and PFS on the intent-to-treat population; secondary endpoints included RR, response duration, and safety. Final analysis was planned at 196 deaths. Results: 675 pts were enrolled at 103 centers worldwide between Jan and Dec 2010. Treatment cohorts were well-balanced. At the pre-planned interim analysis (50% of deaths needed for final analysis), the hazard ratios for OS and PFS were 0.37 (95% CI 0.26 to 0.55; p<0.0001) and 0.26 (95% CI 0.20 to 0.33; p<0.0001), respectively, both in favor of vemurafenib. The confirmed RR was 48.4% and 5.5% to vemurafenib and DTIC, respectively, among the 65% of pts evaluable for RR to date. Benefit in OS, PFS, and RR was seen in all subgroups examined. Due to these data, the DTIC cohort has been allowed to cross over to vemurafenib. At the time of data analysis, 66% of vemurafenib pts and 25% DTIC pts were still on treatment. The most common toxicities of vemurafenib were: diarrhea, rash, alopecia, photosensitivity, fatigue, arthralgia, and keratoacanthoma/skin squamous cell carcinoma. Conclusions: Vemurafenib is associated with significantly improved OS and PFS compared to DTIC in pts with previously untreated, V600EBRAF-mutated metastatic melanoma.

Novel anti-idiotype antibody therapy for lipooligosaccharide-induced experimental autoimmune neuritis: use relevant to Guillain-Barré syndrome

Campylobacteriosis is a frequent antecedent event in Guillain-Barré syndrome (GBS), inducing high-titer serum antibodies for ganglioside antigens in the peripheral nervous system (PNS). Molecular mimicry between the lipooligosaccharide (LOS) component of Campylobacter jejuni and human peripheral nerve gangliosides is believed to play an important role in the pathogenesis of GBS. Conventional treatment strategies for patients with GBS include plasmapheresis, intravenous immunoglobulin (IVIG), and immunosuppression, which are invasive or relatively ineffective. In this study, we used our animal model of GBS, in which Lewis rats were immunized with GD3-like LOS isolated from C.jejuni. The animals developed anti-GD3 ganglioside antibodies and manifested neuromuscular dysfunction. To develop novel therapeutic strategies, we treated the animals by intraperitoneal administration of an anti-GD3 antiidiotype monoclonal antibody (BEC2) that specifically interacts with the pathogenic antibody. The treated animals had a remarkable reduction of anti-GD3 antibody titers and improvement of motor nerve functions. The results suggest that ganglioside mimics, such as antiidiotype antibodies, may be powerful reagents for therapeutic intervention in GBS by neutralizing specific pathogenic antiganglioside antibodies.

Phase II trial of neoadjuvant temozolomide in resectable melanoma patients

BACKGROUND

We treated melanoma patients with temozolomide (TMZ) in the neoadjuvant setting and collected cryopreserved tumor samples before and after treatment. The primary objective was to determine whether the response proportion was higher than previously reported in widely metastatic patients. A secondary objective was to test the feasibility of obtaining adequate tissue before and after treatment for genetic testing.

MATERIALS AND METHODS

Chemotherapy-naive melanoma patients who were candidates for surgical resection were eligible. TMZ was administered orally at 75 mg/m(2)/day for 6 weeks of every 8-week cycle. Cycles were repeated until complete response (CR), progression, or stable disease (SD) for two cycles.

RESULTS

Of 19 assessable patients, 2 had CRs and 1 had partial response. Four patients had SD; 12 progressed. Tumor O-6-methylguanine-DNA methyltransferase (MGMT) promoter was unmethylated in all nine patients analyzed including from the two CR patients. Pretreatment tumor microarray results were obtained in 16 of 19 patients.

CONCLUSIONS

The response proportion to TMZ in the neoadjuvant setting was 16%, not different than in the metastatic setting. Responses were seen even in tumors with a methylated MGMT promoter. Pretreatment cryopreserved tumor adequate for microarray analysis could be obtained in most, but not all, patients. Post-treatment tumor was unavailable in complete responders.

PLX4032, a highly selective V600EBRAF kinase inhibitor: Clinical correlation of activity with pharmacokinetic and pharmacodynamic parameters in a phase I trial

9021

Background: PLX4032 is an oral, highly selective inhibitor of oncogenic V600EBRAF kinase currently in phase I trial. V600EBRAF mutation activates Raf/MEK/ERK pathway in multiple tumor types. We evaluated the relationship between PK, PD (pERK, Ki67, FDG-PET), tumor histology and clinical activity following PLX4032 administration in a phase I trial. Methods: In the phase I trial, 6 melanoma pts with V600EBRAF were treated with PLX4032 daily at several dose levels and tumor biopsies (baseline vs. day 15) were assessed histologically and by semi-quantitative IHC analysis (modified H-score) for pERK and Ki67. The first 4 pts received a crystalline formulation of PLX4032; the last 2 pts received a formulation with increased bioavailability. Plasma PK parameters were collected at frequent time points on Days 1, 8 and 15. FDG-PET was performed on Days 1 and 15 on last 2 pts. Results: In the first 4 pts, no histological changes were observed with treatment and all developed disease progression. All had decreased percentage of Ki67 positive nuclei (pre-Rx, range 20–60%, median 45%; post-Rx, range 5–25%, median 12.5%) and 3 of the 4 had decreased pERK levels (pre-Rx, range 50–100, median 60; post-Rx, range 10–40, median 11). Mean PLX4032 AUC0–24h ∼ 126 μM*h was in the range for preclinical tumor stasis but below the threshold for shrinkage. In the last 2 pts, striking tumor necrosis and tumor melanosis was observed in the post-Rx samples. One pt remains on study with a confirmed PR, the other showed a clinical response before disease progression occurred in cycle 2. The percentage of Ki67 positive nuclei declined substantially (pre-Rx, 30% and 50% to post-Rx, 5% and 3%), as did the levels of pERK in the pt with PR (pre-Rx: 70 to post-Rx: 2). Mean PLX4032 AUC0–24h was well above the preclinical threshold in the range of 500 - 1000 μM*h. Both pts had decreased FDG uptake on D15. Conclusions: Clinical activity of PLX4032 treatment correlates with drug exposure levels as measured by AUC0–24h and was associated with histological changes in V600EBRAF positive melanomas on Day 15. Reduction of pERK, along with evidence of reduced proliferation and FDG uptake was observed. Further analysis of PD markers with additional pts at the MTD is planned.

[Table: see text]

A phase II study of imatinib mesylate (IM) for patients with advanced melanoma harboring somatic alterations of KIT

9001

Background: Three prior phase II studies of Imatinib mesylate (IM) in 62 pts with advanced melanoma reported only 1 response in a pt with acral melanoma. A proportion of melanomas arising from acral, mucosal, and chronic sun damaged (CSD) sites are characterized by KIT mutations (mut) or amplifications (amp) and we hypothesized that this subset of tumors would be sensitive to IM. We thus designed this phase II study of IM restricted to pts with melanoma harboring such alterations in KIT. Methods: Pts with unresectable melanoma arising from acral, mucosal, and CSD sites whose tumor harbored a 4q12 amp by FISH or mut in KIT and who had measureable disease by RECIST were eligible. Pts received IM 400 mg BID continually. Response was assessed every cycle (6 wks). A Simon 2-stage design was employed where initially 16 pts would be treated; if ≥ 2 responses were observed, a total of 25 pts would be enrolled. If ≥5 responses were seen in 25 pts, the study was to be considered positive. Results: Of 81 pt tumors screened, 17 (21%) had a KITmut or amp: 5/22 (23%) acral, 12/45 (27%) mucosal, 0/13 (0%) CSD, 0/1 (0%) unknown primary. 12 (15%) had a mut only; 4 (5%) had an amplification only; 1 (2%) had both. Thus far, 7 have been treated, with 5 currently evaluable for response. Median age: 64 yrs (range, 61–86); 2 male/5 female; median KPS: 90 (range, 80- 90); median # of prior therapies: 1 (range, 0–4). 3 pts (43%) achieved a PR (18 wks - exon 13 mut; 21 wks, ongoing - exon 11 mut; 18 wks, ongoing - exon 11 mut & amp); 2 pts (28%) achieved SD (12 wks - exon 11 mut; 11 wks - amp). 3 pts required a dose reduction to 400 mg QD for rash, GI toxicity and fatigue. 1 pt required a second dose reduction to 300 mg QD for visual changes. Conclusions: In this pt population, 21% of tumors are characterized by mut or amp of KIT. The 3 responses observed have allowed expansion to the second stage of enrollment which is currently on-going. While IM has limited activity in a non-selected melanoma pt population, a substantial proportion of melanomas harboring KIT mut or amp appear to respond. It may be possible to identify appropriate pts prospectively for treatment with IM. (Supported by R01FD003445–01, ASCO YIA, N01CM62206, and the Live4Life Foundation.)

No significant financial relationships to disclose.

Antibody response to GD3 ganglioside is independent of NKT cells

BACKGROUND

NKT cells recognize glycolipids presented by CD1d on antigen-presenting cells (APC) and have been largely characterized by their ability to be activated by alpha-galactosylceramide, a glycolipid not expressed on mammalian cells. We have shown previously that GD3 can be cross-presented by CD1d to NKT cells and is the first tumor-derived glycolipid recognized by NKT cells. But the ability of NKT cells to modulate B-cell responses to tumor glycolipids that are themselves recognized by NKT cells has not been explored.

METHODS

We tested whether NKT cells are required for antibody (Ab) responses to GD3. We immunized wild-type mice, mice deficient in invariant chain NKT cells (iNKT cells) and mice deficient in total NKT cells against GD3. Ab titer against GD3 was measured by ELISA.

RESULTS

We found the IgM and IgG responses against GD3 were similar among the three strains of mice, including the IgG isotypes induced. Pre-expanded NKT cells to GD3 did not affect the anti-GD3 Ab response.

DISCUSSION

We conclude that Ab responses to GD3 are independent of NKT cells and that strategies to manipulate NKT cells in vivo are not likely to enhance the anti-GD3 Ab response induced by vaccines.

Safety and immunogenicity of tyrosinase DNA vaccines in patients with melanoma

3005

Background: T-cell and antibody responses to self antigens on cancer are usually constrained by immunologic tolerance and ignorance. We found that DNA vaccines encoding xenogeneic differentiation antigens, such as tyrosinase (TYR), can mediate tumor protection and regression in implantable mouse models and dogs with spontaneously arising melanoma. Based on this, we conducted a trial of DNA vaccines encoding mouse and human TYR in patients with AJCC stage III/IV melanoma. Methods: HLA-A*0201+ melanoma patients were randomized to 2 different schedules: one group received 3 injections of mouse TYR DNA followed by 3 injections of human TYR DNA while the other group received 3 injections of human TYR DNA followed by 3 injections with the mouse gene. The study was conducted a three different dose levels: 100, 500 and 1,500 mcg DNA/injection, administered IM every 3 weeks. A total of 18 patients were treated, 6 at each dose level being randomized to one of the two schedules. Anti-TYR antibodies and CD8+ T cells recognizing the native human tyrosinase369-377 (YMDGTMSQV) peptide were measured at fixed time points. T-cell responses were monitored with MHC tetramer and intracytoplasmic IFN-γ staining assays using 10-day in vitro stimulation. Multiparametric flow cytometry was performed to further define the phenotype of responding cells. Results: Most toxicities were transient grade I injection site reactions. Seven patients had CD8+ T cell responses, defined as a >3 standard deviation increase in baseline reactivity to the TYR peptide in either the tetramer or intracellular IFN-γ assay. There was no relationship between dose level or assigned schedule and occurrence of T-cell response. Phenotypic characterization of responding T cells showed that most were consistent with an effector memory phenotype including the expression of granzyme B and surface expression of CD107a. No antibody responses were observed. At a median of 42 months of follow-up, median survival has not been reached and 6/18 patients have died from melanoma (1 in the group of patients who had a T cell response and 5 in the non-responders). Conclusions: Mouse and human TYR DNA vaccines were safe and induced CD8+ T cell responses in 7/18 patients. T cells recognizing a native TYR peptide had a phenotype consistent with that of effector memory cells.

No significant financial relationships to disclose.

Clinical results using biochemotherapy as a standard of care in advanced melanoma

Phase II studies of biochemotherapy in metastatic melanoma patients have reported response rates of 47-63%. Even though these were highly selected patients, we were intrigued by these promising response rates and began using this regimen as standard care in advanced melanoma patients. We report the results of the first 65 patients with AJCC stage IV melanoma (n = 57) or unresectable stage III (n = 8) melanoma treated with concurrent biochemotherapy at Memorial Hospital. Treatment was repeated every 3 weeks and patients were assessed for antitumour effects after every other cycle. The overall response rate among the 63 patients evaluable for response was 29% (three complete responses, 15 partial responses). The median duration of responses was 3.7 months. The response rate among previously treated and previously untreated patients was 6% and 38%, respectively. The estimated median survival for all patients was 8.5 months; the median survival for previously untreated patients was 9.2 months. Tumour response did not correlate with survival. Our experience, which is a retrospective evaluation, does not provide support for the routine use of biochemotherapy as standard treatment. The low response rate among previously treated patients indicates that biochemotherapy is not useful as second-line therapy.

High-dose interferon alfa-2b does not diminish antibody response to GM2 vaccination in patients with resected melanoma: results of the Multicenter Eastern Cooperative Oncology Group Phase II Trial E2696

PURPOSE

High-dose interferon alfa-2b (IFNalpha2b) is the only established adjuvant therapy of resectable high-risk melanoma. GM2-KLH/QS-21 (GMK) is a chemically defined vaccine that is one of the best developed of a range of vaccine candidates for melanoma. A single-institution phase III trial conducted at Memorial Hospital served as the impetus for an intergroup adjuvant E1694/S9512/C509801 trial, which recently completed enrollment of 880 patients. To build on the apparent benefit of IFNalpha2b in resectable high-risk American Joint Committee on Cancer (AJCC) stage IIB or III melanoma, this phase II study was designed to evaluate the combination of GMK and IFNalpha2b. The E2696 trial was undertaken to evaluate the toxicity and other effects of the established adjuvant high-dose IFNalpha2b regimen in relation to immune responses to GMK and to evaluate the potential clinical and immunologic effects of the combined therapies.

PATIENTS AND METHODS

This trial enrolled 107 patients with resectable high- or very high-risk melanoma (AJCC stages IIB, III, and IV).

RESULTS

The results demonstrate that IFNalpha2b does not significantly inhibit immunoglobulin M or G serologic responses to the vaccine and that the combination of high-dose IFNalpha2b and GMK is well tolerated in this patient population.

CONCLUSION

Cox analysis of the results of the combination with IFNalpha2b show improvement in the relapse-free survival of patients with very high-risk melanoma (including those with resectable M1 disease).

Paucity of functional T-cell memory to melanoma antigens in healthy donors and melanoma patients

The functional characteristics of CD8+ T cells specific for melanoma antigens (MAs) have often been defined after in vitro culture using nonprofessional antigen-presenting cells. We have examined CD8+ T-cell immunity to MAs and a viral antigen (influenza) in uncultured T cells of healthy donors and melanoma patients using autologous, mature, monocyte-derived dendritic cells (DCs) pulsed with peptide antigens and viral vectors. Antigen-specific IFN-gamma-producing T cells reactive with HLA-A*0201-restricted peptides from four melanoma antigens (MelanA/MART-1, MAGE-3, tyrosinase, and gp100) were detected only at low frequencies (<30 per 2 x 10(5) peripheral blood mononuclear cells for each of the MAs) from HLA-A2.1-positive healthy donors (n = 12) and patients with stages III/IV melanoma (n = 8). Detection of MA-specific, but not influenza matrix peptide (Flu-MP)-specific, T cells required a high concentration (10 microg/ml) of the peptide in this assay. Furthermore, these T cells did not recognize endogenously processed antigen on tumor cell lines or cells infected with viral vectors capable of expressing MAs. The use of autologous, mature DCs led to a significant increase in the number of Flu-MP, but not MA-specific, T cells in 16-h ELISPOT assays for both melanoma patients and healthy donors. In 1-week cocultures with DCs pulsed with 10 microg/ml peptide, MelanA/MART-1-specific T cells did not readily proliferate or differentiate into lytic effectors, in contrast to strong influenza-specific lytic responses. Therefore, despite distinct memory responses to influenza antigens, melanoma patients and healthy controls have a paucity of MA-reactive memory T cells, failing to rapidly generate IFN-gamma-secreting lytic effectors in short-term assays, even when stimulated by DCs.

Vaccination with a bivalent G(M2) and G(D2) ganglioside conjugate vaccine: a trial comparing doses of G(D2)-keyhole limpet hemocyanin

Immunization with GMK vaccine (G(M2) ganglioside conjugated to keyhole limpet hemocyanin mixed with QS-21 adjuvant) induces anti-G(M2) antibodies in close to 100% of patients. We found previously that anti-G(D2) antibodies could be induced in some patients using G(D2)-keyhole limpet hemocyanin + QS-21 (GDK). In this trial, we wished: (a) to determine whether immunization with both GMK and GDK vaccines could induce antibodies against both G(M2) and G(D2); and (b) to determine the optimal dose of GDK. Thirty-one patients with melanoma or sarcoma who had no evidence of disease after complete surgical resection were immunized with both GMK (30 microg of G(M2)) and GDK on weeks 1, 2, 3, 4, 12, 24, and 36. Patients were assigned to one of five GDK dose levels (3, 10, 30, 70, or 130 microg of G(D2)). Anti-G(M2) IgM or IgG were induced in 97% of patients. The dose of GDK did not affect the anti-G(M2) response, although at the highest GDK dose level, 3 of 7 patients did not make anti-G(M2) IgG. GDK was less immunogenic; overall 45% of patients developed either IgM or IgG against G(D2). At GDK doses of 30 or 70 microg, 8 of 11 patients (73%) made either IgM or IgG anti-G(D2) antibodies. We conclude that both GMK and GDK vaccines can induce antibodies against G(M2) and G(D2) in a majority of patients and are safe. The optimal dose of GDK appears to be either 30 or 70 microg when administered with GMK vaccine.

Evaluation of CD8(+) T-cell frequencies by the Elispot assay in healthy individuals and in patients with metastatic melanoma immunized with tyrosinase peptide

The lack of reproducible, quantitative assays for T-cell responses has been a limitation in the development of cancer vaccines to elicit T-cell immunity. We utilized the Elispot assay, which allows a quantitative and functional assessment of T cells directed against specific peptides after only brief in vitro incubations. CD8(+) T-cell reactivity was determined with an interferon (IFN)-gamma Elispot assay detecting T cells at the single cell level that secrete IFN-gamma. We studied both healthy individuals and patients with melanoma. Healthy HLA-A*0201-positive individuals showed a similar mean frequency of CD8(+) cells recognizing a tyrosinase peptide, YMDGTMSQV, when compared with melanoma patients prior to immunization. The frequencies of CD8(+) cells recognizing the tyrosinase peptide remained relatively constant over time in healthy individuals. Nine HLA-A*0201-positive patients with stage IV metastatic melanoma were immunized intradermally with the tyrosinase peptide together with the immune adjuvant QS-21 in a peptide dose escalation study with 3 patients per dose group. Two patients demonstrated a significant increase in the frequency of CD8(+) cells recognizing the tyrosinase peptide during the course of immunization, from approx. 1/16,000 CD8(+) T cells to approx. 1/4,000 in the first patient and from approx. 1/14,000 to approx. 1/2,000 in the second patient. These results demonstrate that modest expansion of peptide-specific CD8(+) T cells can be generated in vivo by immunization with peptide plus QS-21 in at least a subset of patients with melanoma.

Systemic chemotherapy

The main use of systemic chemotherapy in metastatic melanoma remains palliative. Dacarbazine (dimethyl-1-triazeno imidazole-4-carboxamide [DTIC]) is the standard chemotherapy agent for advanced disease. The combination chemotherapy and biochemotherapy regimens have achieved higher response rates, but have not led to durable remission or improved survival. The field of systemic therapy remains in need of a more effective and less toxic treatment strategy.

Induction of antibodies against GM2 ganglioside by immunizing melanoma patients using GM2-keyhole limpet hemocyanin + QS21 vaccine: a dose-response study

In a previous randomized Phase III trial (P. O. Livingston et al, J. Clin. Oncol., 12: 1036-1044, 1994), we demonstrated that immunization with GM2 and bacille Calmette-Guerin reduced the risk of relapse in stage III melanoma patients who were free of disease after surgical resection and who had no preexisting anti-GM2 antibodies. That vaccine formulation induced IgM anti-GM2 antibodies in 74% but induced IgG anti-GM2 antibodies in only 10% of the patients. To optimize the immune response against GM2, a reformulated vaccine was produced conjugating GM2 to keyhole limpet hemocyanin (KLH) and using the adjuvant QS21 (GM2-KLH/QS21). In pilot studies, 70 microg of vaccine induced IgG anti-GM2 antibodies in 76% of the patients. We wished to define the lowest vaccine dose that induced consistent, high-titer IgM and IgG antibodies against GM2. Fifty-two melanoma patients who were free of disease after resection but at high risk for relapse were immunized with GM2-KLH/QS21 vaccine at GM2 doses of 1, 3, 10, 30, or 70 ILg on weeks 1, 2, 3, 4, 12, 24, and 36. Serum collected at frequent and defined intervals was tested for anti-GM2 antibodies. Overall, 88% of the patients developed IgM anti-GM2 antibodies; 71% also developed IgG anti-GM2 antibodies. GM2-KLH doses of 3-70 microg seemed to be equivalent in terms of peak titers and induction of anti-GM2 antibodies. At the 30-microg dose level, 50% of the patients developed complement fixing anti-GM2 antibodies detectable at a serum dilution of 1:10. We conclude that the GM2-KLH/QS21 formulation is more immunogenic than our previous formulation and that 3 microg is the lowest dose that induces consistent, high-titer IgM and IgG antibodies against GM2.

Prophylactic recombinant epoetin alfa markedly reduces the need for blood transfusion in patients with metastatic melanoma treated with biochemotherapy

Treatment of metastatic melanoma with biochemotherapy results in the rapid onset of anemia, requiring blood transfusion in 9 of 13 (69%) patients. Prophylactic use of weekly subcutaneous recombinant epoetin alfa eliminated the need for transfusion in all but 1 of 21 (5%) patients.

Intradermal injection of granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with metastatic melanoma recruits dendritic cells

Dendritic cells (DCs) are the main antigen-presenting cells in the skin. We hypothesized that intradermal (i.d.) injection of granulocyte-macrophage colony-stimulating factor (GM-CSF) would recruit DCs into melanoma skin metastases and enhance autologous melanoma antigen presentation to host T cells. Sixteen patients with cutaneous or subcutaneous melanoma metastases were treated with GM-CSF injected i.d. into a single dermal metastasis and into a normal skin site for 10 consecutive days at one of four dose levels (10, 20, 40, or 80 microg/injection). Pretreatment and post-treatment skin and tumor biopsies were stained for a panel of T-cell, B-cell, macrophage, and DC immunohistochemical markers. Positive cells were quantitated in a blinded fashion. There was a significant increase in the number of DCs (HLA-DR+, S100+, factor XIIIa+) and CD45R0+ T cells in the skin and in the tumors Injected with GM-CSF at all dose levels. Uninjected control tumors showed no increase in HLA-DR+ cells or T-cell infiltrate, but did show an Increase in S100+ and factor XIIIa+ cells, suggesting a non-DC population. ID GM-CSF administered in this manner recruited DCs into melanoma tumors and normal skin. Although no antitumor effects were seen, this represents a potential method of preparing skin sites for vaccine delivery.

Phase III multicenter randomized trial of the Dartmouth regimen versus dacarbazine in patients with metastatic melanoma

PURPOSE

Several single-institution phase II trials have reported that the Dartmouth regimen (dacarbazine, cisplatin, carmustine, and tamoxifen) can induce major tumor responses in 40% to 50% of stage IV melanoma patients. This study was designed to compare the overall survival time, rate of objective tumor response, and toxicity of the Dartmouth regimen with standard dacarbazine treatment in stage IV melanoma patients.

PATIENTS AND METHODS

In this multicenter phase III trial, 240 patients with measurable stage IV melanoma were randomized to receive the Dartmouth regimen (dacarbazine 220 mg/m(2) and cisplatin 25 mg/m(2) days 1 to 3, carmustine 150 mg/m(2) day 1 every other cycle, and tamoxifen 10 mg orally bid) or dacarbazine 1, 000 mg/m(2). Treatment was repeated every 3 weeks. Patients were observed for tumor response, survival time, and toxicity.

RESULTS

Median survival time from randomization was 7 months; 25% of the patients survived > or = 1 year. There was no difference in survival time between the two treatment arms when analyzed on an intent-to-treat basis or when only the 231 patients who were both eligible and had received treatment were considered. Tumor response was assessable in 226 patients. The response rate to dacarbazine was 10.2% compared with 18.5% for the Dartmouth regimen (P =.09). Bone marrow suppression, nausea/vomiting, and fatigue were significantly more common in the Dartmouth arm.

CONCLUSION

There was no difference in survival time and only a small, statistically nonsignificant increase in tumor response for stage IV melanoma patients treated with the Dartmouth regimen compared with dacarbazine. Dacarbazine remains the reference standard treatment for stage IV melanoma.

Long survival of patients with small cell lung cancer after adjuvant treatment with the anti-idiotypic antibody BEC2 plus Bacillus Calmette-Guérin

Despite active therapies for small cell lung cancer (SCLC), most patients relapse and die of the disease. The present study evaluates immunization using the anti-idiotypic antibody BEC2, which mimics the ganglioside GD3 expressed on the surface of most SCLC tumors, combined with Bacillus Calmette-Guérin (BCG) as an immune adjuvant. We hypothesized that active immunization could alter the natural history of the disease. Fifteen patients who had completed standard therapy for SCLC received a series of five intradermal immunizations consisting of 2.5 mg of BEC2 plus BCG over a 10-week period. Blood was collected for serological analysis, and outcome was monitored. All patients developed anti-BEC2 antibodies, despite having received chemotherapy with or without thoracic radiation. We detected anti-GD3 antibodies in five patients, including those with the longest relapse-free survival. The median relapse-free survival for patients with extensive stage disease is 11 months and has not been reached for patients with limited stage disease (>47 months), with only one of seven patients having relapsed after a median follow-up of 47 months. Immunization of patients with SCLC after standard therapy using BEC2 plus BCG can induce anti-GD3 antibodies and is safe. The survival and relapse-free survival in this group of patients are substantially better than those observed in a prior group of similar patients. A Phase III trial is being conducted to evaluate BEC2 plus BCG as adjuvant therapy after chemotherapy and irradiation.

The role of homophilic binding in anti-tumor antibody R24 recognition of molecular surfaces. Demonstration of an intermolecular beta-sheet interaction between vh domains

The murine antibody R24 and mouse-human Fv-IgG1(kappa) chimeric antibody chR24 are specific for the cell-surface tumor antigen disialoganglioside GD3. X-ray diffraction and surface plasmon resonance experiments have been employed to study the mechanism of "homophilic binding," in which molecules of R24 recognize and bind to other molecules of R24 though their heavy chain variable domains. R24 exhibits strong binding to liposomes containing disialoganglioside GD3; however, the kinetics are unusual in that saturation of binding is not observed. The binding of chR24 to GD3-bearing liposomes is significantly weaker, suggesting that cooperative interactions involving antibody constant regions contribute to R24 binding of membrane-bound GD3. The crystal structures of the Fabs from R24 and chR24 reveal the mechanism for homophilic binding and confirm that the homophilic and antigen-binding idiotopes are distinct. The homophilic binding idiotope is formed largely by an anti-parallel beta-sheet dimerization between the H2 complementarity determining region (CDR) loops of two Fabs, while the antigen-binding idiotope is a pocket formed by the three CDR loops on the heavy chain. The formation of homophilic dimers requires the presence of a canonical conformation for the H2 CDR in conjunction with participation of side chains. The relative positions of the homophilic and antigen-binding sites allows for a lattice of GD3-specific antibodies to be constructed, which is stabilized by the presence of the cell membrane. This model provides for the selective recognition by R24 of cells that overexpress GD3 on the cell surface.

Immunization of melanoma patients with BEC2-keyhole limpet hemocyanin plus BCG intradermally followed by intravenous booster immunizations with BEC2 to induce anti-GD3 ganglioside antibodies

BEC2 is an anti-idiotypic mouse monoclonal antibody that mimics GD3 ganglioside. Previous clinical trials demonstrated that intradermal immunization using 2.5 mg of BEC2 with BCG or i.v. immunization with 10 mg of BEC2 can induce anti-GD3 antibodies in a subset of patients. We hypothesized that combining these two immunization strategies might be more effective in inducing anti-GD3 antibodies and that conjugation of BEC2 to keyhole limpet hemocyanin (KLH) would further enhance the immunogenicity of BEC2. In this clinical trial, 18 melanoma patients who were free of disease after complete surgical resection within 1-6 months received intradermal immunizations on weeks 0, 2, 4, 6, and 10 with 2.5 mg of BEC2 conjugated to KLH and mixed with BCG (BEC2-KLH/BCG). Booster immunizations of 10 mg of unconjugated BEC2 were administered i.v. on weeks 24, 37, and 50. Four of 18 patients (22%) developed IgM anti-GD3 antibodies. No IgG anti-GD3 antibodies were detected. All four responding patients developed anti-GD3 IgM during immunization with BEC2-KLH/BCG; only one patient demonstrated a reboost of the IgM anti-GD3 titer during the i.v. immunizations. Thirteen of the patients are free of melanoma (3 after undergoing re-resection for local relapse); 14 patients (78%) remain alive with a median follow-up of 28 months. These results confirm our previous trial, showing that BEC2 with BCG can induce anti-GD3 antibodies in patients. The data do not provide evidence that conjugation to KLH increases the immunogenicity of BEC2 when it is administered with BCG.

Phase I study of R24 in patients with metastatic melanoma including evaluation of immunologic parameters

R24 is a mouse IgG3 monoclonal antibody with specificity for the disialoganglioside GD3. Most human melanomas have substantial surface GD3; in addition, a significant proportion of T lymphocytes display surface GD3. In a phase I study, we have investigated the toxicity and effect on selected immunological parameters of three dose levels of R24 given intravenously daily for five days (10 mg/m2/d, 30 mg/m2/d and 50 mg/m2/d) to patients with advanced melanoma. R24 administration neither consistently diminished nor augmented expression of delayed type hypersensitivity (DTH) skin reactions to anergy panel antigens or to a contact allergen dinitrofluorobenzene. R24 was infrequently found on tumor cells, or on lymphocytes from DTH biopsies, despite measurable serum levels of R24. The 30 mg/m2/d dose of R24 produced a statistically significant drop in peripheral blood lymphocytes on treatment Day 5. Likewise, on Day 5 there was a modest but statistically significant decrement in the proportion of circulating cells which were R24+. While there was one mixed response, there were no complete or partial tumor regressions in the R24 treated patients; there was no evident clinical benefit from the R24 therapy. The toxicity of the R24 at the higher dose levels can be very substantial. One patient, on the highest dose level, died on the 4th day of R24 treatment; in the absence of a plausible alternative explanation, a relationship of the death to the administered R24 must be considered. A precipitous drop in serum albumin coincident with R24 administration was found in all cases; this effect has not been previously reported with R24.

Anti-melanoma effects of R24, a monoclonal antibody against GD3 ganglioside

R24, a mouse monoclonal antibody against GD3 ganglioside, is potent at mediating in vitro effector functions such as human complement-mediated cytotoxicity and antibody-dependent cellular cytotoxicity, and can block melanoma tumor growth in animal models. Because of these properties and the fact that GD3 is abundantly expressed on virtually all melanomas but is found on few normal tissues, R24 has been tested in a series of clinical trials in patients with metastatic melanoma. As a single agent, R24 can induce responses in patients treated with metastatic melanoma. Overall, there have been 10 responders out of 103 patients reported; two responses have been complete responses. Responses have largely occurred in patients treated with intermediate doses of R24 and have included complete responses. Combining R24 with either cytotoxic drugs or cytokines has not increased this response rate, although one trial with R24 and interleukin-2 resulted in a 43% response rate and merits further investigation. Local-regional treatments R24 (intratumor injections, regional limb perfusion, intrathecal administration) have also been attempted in a small number of patients and responses have been described. Taken together, multiple centers have reported responses in patients with metastatic melanoma treated with R24.

Administration of R24 monoclonal antibody and low-dose interleukin 2 for malignant melanoma

R24 is a monoclonal antibody that recognizes the disialoganglioside GD3 expressed on the surface of malignant melanoma cells. Once bound, it can mediate destruction of these cells through both complement-mediated lysis and antibody-dependent cellular cytotoxicity. Agents such as interleukin 2 (IL-2), which can augment effector cell function and promote destruction of antibody-coated tumor cells, might produce improved antitumor responses when combined with R24. In this series, we evaluated the combination of R24 and IL-2 in a Phase 1b study in patients with metastatic melanoma. Twenty-eight patients with metastatic melanoma were entered into the protocol at two institutions. Patients received 8 weeks of IL-2 by continuous i.v. infusion at a dose (4.5 x 10(5) Amgen units/m2/day) designed to selectively expand natural killer (NK) cells. In weeks 5 and 6, patients received R24 for a total of four doses. Twenty-four h after each R24 infusion, patients received a 2-h bolus dose of IL-2 to help promote activity of NK effectors against antibody-coated melanoma targets. Additional IL-2 boluses were administered in weeks 7 and 8. Doses were escalated through two bolus doses of R24 (5 or 15 mg/m2) and two bolus doses of IL-2 (2.5 or 5.0 x 10(5) units/m2). Although one patient experienced severe capillary leak syndrome during IL-2, therapy was otherwise well tolerated. At the higher dose level of R24, two of four patients experienced transient but severe abdominal and chest discomfort, necessitating dose reduction. One patient with ocular melanoma and liver metastases had a partial response. Two additional patients had minor responses. A dramatic increase in NK cell number was noted as a result of treatment, as was augmentation of cytolytic activity against cultured NK-sensitive targets. Antibody-dependent cellular cytotoxicity against cultured melanoma cells in the presence of exogenous R24 or in the presence of serum obtained from patients following R24 infusion also increased during treatment. Our experience indicates that R24 and low-dose IL-2 can be safely combined in patients with metastatic melanoma and that this combination can promote destruction of cultured melanoma cells. The clinical activity of this combination against ocular melanoma may merit further investigation.

Medical treatment of metastatic melanoma

The role of combination chemotherapy in the treatment of metastatic melanoma is still a matter of controversy because of the lack of prospective trials directly demonstrating increased response rates and improved survival compared with DTIC alone. Nevertheless, several three-drug regimens have reported response rates between 30% and 50% in single-institution studies. The duration of response medians of these regimens ranges between 6 and 9 months. However, the survival medians of 6 to 11 months are not substantially better than those of DTIC alone. However, survival at 1 and 2 years following initiation of therapy may more clearly demonstrate an impact of therapies for metastatic melanoma.

Characterization of an Ig VH idiotope that results in specific homophilic binding and increased avidity for antigen

mAb against GD3 ganglioside demonstrate homophilic binding in which soluble anti-GD3 mAb bind, through the GD3 binding site, to a VH idiotope (designated IdHOM) on solid phase anti-GD3 mAb. In this way, homophilic binding provides a mechanism for amplifying the binding of mAb to cell surface GD3. We show that serine 52a, within CDR2, is required for IdHOM expression, homophilic binding, and high avidity binding to cell surface GD3. Computer modeling based on the crystal structure of anti-GD3 mAb R24 showed serine 52a situated at the mouth of the GD3 binding pocket, but not directly involved with GD3 binding. Substitutions at position 52a predicted to maintain the GD3 binding pocket (e.g., threonine) resulted in the loss of IdHOM expression and homophilic binding and markedly decreased binding to cell surface GD3, but maintained low avidity GD3 binding as measured by ELISA. All other substitutions at position 52a were predicted to significantly distort the GD3 binding pocket and resulted in the loss of both homophilic binding and any detectable avidity for GD3. We have structurally defined IdHOM and conclude that this idiotope is not required for the GD3 binding pocket, but that the idiotope is necessary for homophilic binding, which is required for high avidity binding to cell surface GD3. We speculate that selection of certain VH genes may result in the expression of idiotopes that allow homophilic binding, and this may represent a general mechanism for increasing the avidity of Abs against T cell-independent Ags.

Characterization of an Ig VH idiotope that results in specific homophilic binding and increased avidity for antigen

mAb against GD3 ganglioside demonstrate homophilic binding in which soluble anti-GD3 mAb bind, through the GD3 binding site, to a VH idiotope (designated IdHOM) on solid phase anti-GD3 mAb. In this way, homophilic binding provides a mechanism for amplifying the binding of mAb to cell surface GD3. We show that serine 52a, within CDR2, is required for IdHOM expression, homophilic binding, and high avidity binding to cell surface GD3. Computer modeling based on the crystal structure of anti-GD3 mAb R24 showed serine 52a situated at the mouth of the GD3 binding pocket, but not directly involved with GD3 binding. Substitutions at position 52a predicted to maintain the GD3 binding pocket (e.g., threonine) resulted in the loss of IdHOM expression and homophilic binding and markedly decreased binding to cell surface GD3, but maintained low avidity GD3 binding as measured by ELISA. All other substitutions at position 52a were predicted to significantly distort the GD3 binding pocket and resulted in the loss of both homophilic binding and any detectable avidity for GD3. We have structurally defined IdHOM and conclude that this idiotope is not required for the GD3 binding pocket, but that the idiotope is necessary for homophilic binding, which is required for high avidity binding to cell surface GD3. We speculate that selection of certain VH genes may result in the expression of idiotopes that allow homophilic binding, and this may represent a general mechanism for increasing the avidity of Abs against T cell-independent Ags.

Immunization of melanoma patients with BEC2 anti-idiotypic monoclonal antibody that mimics GD3 ganglioside: enhanced immunogenicity when combined with adjuvant

Previous attempts to immunize melanoma patients against GD3 ganglioside have been unsuccessful because of the poor immunogenicity of GD3. BEC2, an anti-idiotypic monoclonal antibody that mimics GD3, can induce anti-GD3 IgG in rabbits. Since clinical trials with BEC2 in melanoma patients demonstrated that BEC2 alone is not highly immunogenic, we have carried out sequential clinical trials exploring the use of two immunological adjuvants, BCG and QS21, administered with BEC2. Melanoma patients free of disease after surgical resection but at high risk for recurrence were immunized either with BEC2/BCG (14 patients) or BEC2/QS21 (6 patients). All patients developed high-titer IgG antibodies against BEC2, demonstrating that both adjuvants effectively enhanced the immunogenicity of BEC2. Anti-GD3 antibodies were induced in 3 of 14 patients immunized with BEC2/BCG; no patient immunized with BEC2/QS21 developed detectable anti-GD3 antibodies. After a median follow-up of 2.4 years, 71% of the patients immunized with BEC2/BCG remain alive and 64% are free of disease. In patients immunized with BEC2/BCG, no apparent association was observed between class II HLA type and either development of anti-GD3 antibodies or survival. We are encouraged by the results with BEC2/BCG, which suggest that further enhancement of the immune response to BEC2 will result in more frequent anti-GD3 antibody responses among immunized patients.

Phase I study of continuous-infusion recombinant macrophage colony-stimulating factor in patients with metastatic melanoma

Macrophage colony-stimulating factor (M-CSF) is a lineage-specific, homodimeric growth factor that supports the proliferation and maturation of bone marrow progenitors and the survival and function of mononuclear/macrophage cells. In vitro studies have demonstrated antitumor activity of macrophage colony-stimulating factor-treated monocytes against melanoma target cells. A Phase I study was conducted by administering the glycosylated form of the protein to patients with metastatic melanoma as two 7-day continuous i.v. infusions separated by a 2-week rest. Cohorts of three patients per dose level received escalating doses of 10-160 microgram/kg/day. Safety, clinical, and biological effects were evaluated. The infusions were well tolerated with occasional maximum grade 2 nonhematological toxicity. Rapidly reversible thrombocytopenia was the major hematological adverse effect. Its etiology may in part be explained by proliferation and activation of monocyte/macrophage cells in bone marrow samples. Evidence for a biological effect on tumors was suggested by the delayed, complete disappearance of multiple lesions in one patient and a decrease in the size of one marker lesion in a second patient with a mixed response. Fasting serum cholesterol levels decreased during the infusions and may represent an additional therapeutic application for this growth factor.

Anti-idiotypic monoclonal antibody cancer vaccines

Anti-idiotypic monoclonal antibodies (MAb) can mimic both protein and non-protein antigenic epitopes. In animal models, and now in patients, it is possible to induce immune responses against tumor antigens using anti-idiotypic MAb vaccines. While it is not clear how the efficacy of anti-idiotypic MAb vaccines compares with the efficacy of vaccines constructed from antigen, there are two situations where anti-idiotypic vaccines have potential advantages: (1) when the antigen is not readily available in sufficient quantities or purity, and (2) when the antigen is a non-protein. Clinical trials are underway using anti-idiotypic MAb vaccines in both of these situations.

A phase I study of anti-GD3 ganglioside monoclonal antibody R24 and recombinant human macrophage-colony stimulating factor in patients with metastatic melanoma

BACKGROUND

Macrophages activated by macrophage-colony stimulating factor (M-CSF) are potent immune effector cells and can mediate both in vitro cytotoxicity and antitumor effects in vivo. A Phase I trial combining M-CSF with R24, a mouse monoclonal antibody against GD3 ganglioside that has been shown to localize to melanoma tumors, induce inflammation at tumor sites, and result in major tumor responses in some patients with melanoma was performed.

METHODS

Nineteen patients with metastatic melanoma received a 14-day continuous intravenous infusion of 80 micrograms/kg/day of recombinant human M-CSF. R24 was administered daily by intravenous infusion on days 6-10 at doses of 1, 3, 10, 30, and 50 micrograms/m2/day.

RESULTS

All patients developed pruritus and urticaria; 13 patients developed transient thrombocytopenia less than 100,000/mm3. The maximum tolerated dose was not reached. All patients developed a monocytosis characterized by increased expression of the antigen HLA-DR and decreased expression of CD14, a phenotype reported to represent a subpopulation of monocytes active in mediating antibody-directed cellular cytotoxicity. Other biologic effects of treatment included marked but transient decreases in total cholesterol, low density lipoprotein, and high density lipoprotein. Three patients experienced tumor regression in breast, liver, and lymph node metastases and received a second course of therapy. Six of the 19 patients, one of whom received no further therapy, survived more than 2 years and 4 of these patients remain alive 24 to 37 months after treatment. Of the six patients with liver metastases, three (50%) survived more than 2.5 years and one remains alive at 37+ months.

CONCLUSIONS

Combination therapy with R24 and M-CSF resulted in both clinical and biologic effects that warrant further investigation of this combination.

Rejection of mouse melanoma elicited by local secretion of interleukin-2: implicating macrophages without T cells or natural killer cells in tumor rejection

Tumor cells transduced with cytokine genes provide a model to study host-effector mechanisms involved in tumor rejection. Local IL-2 production within a tumor site mimics a specific helper-T-cell response, bypassing an immunization phase. Growth of mouse B16F10 melanomas transduced with interleukin-2 (IL-2) in syngeneic hosts were significantly delayed. IL-2-producing B16F10 cells were super-transduced with interferon-gamma to up-regulate expression of major-histocompatibility-complex (MHC) antigens. Expression of class-I- or class-II-MHC molecules did not augment tumor rejection of IL-2-secreting tumor cells. Rejection of IL-2-transduced B16F10 cells in syngeneic mice was unaffected by depletion of CD8+ T-cell and NK1.1+ natural-killer (NK) cell populations. Tumor rejection occurred in SCID mice even after depletion of NK1.1+ cells, confirming that T cells and NK cells were not required for tumor rejection. Histologic examination of sites of tumor rejection showed inflammation, characterized by infiltrates of macrophages, occasional neutrophils, and areas of necrosis. When mice were treated systemically with macrophage-colony-stimulating factor to expand monocyte pools, tumor rejection was significantly augmented further. This study shows that in situ IL-2 production can result in tumor rejection mediated by inflammatory events, possibly involving macrophages, and mimicking a delayed-type hypersensitivity (DTH) response even in the absence of T cells and NK cells. Furthermore, tumor rejection can be enhanced by systemic administration of a cytokine to expand potential inflammatory cell populations.

Reactivity of autologous CD4+ T lymphocytes against human melanoma. Evidence for a shared melanoma antigen presented by HLA-DR15

Reactivity of CD8+ T lymphocytes against human melanoma has been extensively characterized, but little is known about melanoma Ags recognized by CD4+ lymphocytes. We have identified CD4+ CTL that recognize shared melanoma Ag(s) expressed by autologous melanoma cells and a subset of allogeneic melanomas. The same Ag(s) was shared by autologous and positive allogeneic melanomas by cross-blocking experiments. Cytotoxicity was directed against epitopes presented by HLA-DR on target melanoma cells, and allelic typing revealed that cytotoxicity was restricted through HLA-DR15. These CD4+ T cells released IFN-gamma, IL-4, and TNF-alpha, but not IL-2, in response to HLA-DR15+ target cells. CD4+ T cells did not lyse DR15+ nonmelanoma cell types, including melanocytes or fibroblasts (induced to express HLA-DR by IFN-gamma). Thus, by cytotoxicity assays, shared Ags were only recognized on melanoma cells but not on normal melanocytes. In summary, this analysis shows that melanoma cells share an Ag that is presented by HLA-DR15.

Reactivity of autologous CD4+ T lymphocytes against human melanoma. Evidence for a shared melanoma antigen presented by HLA-DR15

Reactivity of CD8+ T lymphocytes against human melanoma has been extensively characterized, but little is known about melanoma Ags recognized by CD4+ lymphocytes. We have identified CD4+ CTL that recognize shared melanoma Ag(s) expressed by autologous melanoma cells and a subset of allogeneic melanomas. The same Ag(s) was shared by autologous and positive allogeneic melanomas by cross-blocking experiments. Cytotoxicity was directed against epitopes presented by HLA-DR on target melanoma cells, and allelic typing revealed that cytotoxicity was restricted through HLA-DR15. These CD4+ T cells released IFN-gamma, IL-4, and TNF-alpha, but not IL-2, in response to HLA-DR15+ target cells. CD4+ T cells did not lyse DR15+ nonmelanoma cell types, including melanocytes or fibroblasts (induced to express HLA-DR by IFN-gamma). Thus, by cytotoxicity assays, shared Ags were only recognized on melanoma cells but not on normal melanocytes. In summary, this analysis shows that melanoma cells share an Ag that is presented by HLA-DR15.

Mapping effector functions of a monoclonal antibody to GD3 by characterization of a mouse-human chimeric antibody

R24, a mouse monoclonal antibody against GD3 ganglioside, exhibits a wide range of in vitro effector functions. It also has the ability to bind to itself, presumably through homophilic Fab-Fab interactions, which have been proposed to contribute to its high relative avidity for GD3 and to its effector function activity. It is not known which of these characteristics is necessary for the antitumor effects observed in melanoma patients treated with R24. A mouse-human chimeric R24 (chR24) molecule has been constructed in which the GD3-binding site is preserved. Chimeric R24 demonstrates a lower level of binding to GD3 than does mouse R24 suggesting that there may be some differences between the GD3-binding sites of the two mAb or that Fc determinants can contribute to R24 avidity for GD3. The property of homophilic binding is retained by chR24, demonstrating formally that homophilic binding of R24 involves interactions between variable domains. Both R24 and chR24 fix human complement and mediate antibody-dependent cellular cytotoxicity although chR24 was slightly less efficient at the latter. Unlike R24, chR24 was not able to inhibit melanoma cell attachment to plastic surfaces and was not able to activate human T lymphocytes. We hypothesize that chR24 does not bind to GD3 with an avidity high enough to mediate these effector functions.