Developing idiotype vaccines for lymphoma: from preclinical studies to phase III clinical trials

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

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

Idiotype vaccines produced with a non-cytopathic alphavirus self-amplifying RNA vector induce antitumor responses in a murine model of B-cell lymphoma

A promising therapy for patients with B-cell lymphoma is based on vaccination with idiotype monoclonal antibodies (mAbs). Since idiotypes are different in each tumor, a personalized vaccine has to be produced for each patient. Expression of immunoglobulins with appropriate post-translational modifications for human use often requires the use of stable mammalian cells that can be scaled-up to reach the desired level of production. We have used a noncytopathic self-amplifying RNA vector derived from Semliki Forest virus (ncSFV) to generate BHK cell lines expressing murine follicular lymphoma-derived idiotype A20 mAb. ncSFV/BHK cell lines expressed approximately 2 mg/L/24 h of A20 mAb with proper quaternary structure and a glycosylation pattern similar to that of A20 mAb produced by hybridoma cells. A20 mAb purified from the supernatant of a ncSFV cell line, or from the hybridoma, was conjugated to keyhole limpet hemocyanin and used to immunize Balb/c mice by administration of four weekly doses of 25 µg of mAb. Both idiotype mAbs were able to induce a similar antitumor protection and longer survival compared to non-immunized mice. These results indicate that the ncSFV RNA vector could represent a quick and efficient system to produce patient-specific idiotypes with potential application as lymphoma vaccines.

Therapeutic vaccines for aggressive B-cell lymphoma

Diffuse large B-cell lymphoma (DLBCL) is the most common aggressive B-cell lymphoma and highly heterogeneous disease. With the standard immunochemotherapy, anti-CD20 antibody rituximab (R-) plus CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone) chemotherapy, 30-40% of DLBCLs are refractory to initial immunochemotherapy or experience relapse post-therapy with poor clinical outcomes despite salvage therapies. Mechanisms underlying chemoresistance and relapse are heterogeneous across DLBCL and within individual patients, representing hurdles for targeted therapies targeting a specific oncogenic signaling pathway. In recent years, paradigm-shifting immunotherapies have shown impressive efficacy in various cancer types regardless of underlying oncogenic mechanisms. Vaccines are being developed for DLBCL to build protective immunity against relapse after first complete remission and to promote antitumor immune responses synergizing with immune checkpoint inhibitors to treat refractory/relapsed patients. This article provides a brief review of current progress in vaccine development in DLBCL and discussion on immunologic mechanisms underlying the therapeutic effectiveness and resistance.

Brief Communication; A Heterologous Oncolytic Bacteria-Virus Prime-Boost Approach for Anticancer Vaccination in Mice

Supplemental Digital Content is available in the text.

Anticancer vaccination is becoming a popular therapeutic approach for patients with cancers expressing common tumor antigens. One variation on this strategy is a heterologous virus vaccine where 2 viruses encoding the same tumor antigen are administered sequentially to prime and boost antitumor immunity. This approach is currently undergoing clinical investigation using an adenovirus (Ad) and the oncolytic virus Maraba (MRB). In this study, we show that Listeria monocytogenes can be used in place of the Ad to obtain comparable immune priming efficiency before MRB boosting. Importantly, the therapeutic benefits provided by our heterologous L. monocytogenes-MRB prime-boost strategy are superior to those conferred by the Ad-MRB combination. Our study provides proof of concept for the heterologous oncolytic bacteria-virus prime-boost approach for anticancer vaccination and merits its consideration for clinical testing.

New developments in immunotherapy for lymphoma

The development of immunotherapies for lymphoma has undergone a revolutionary evolution over the past decades. Since the advent of rituximab as the first successful immunotherapy for B-cell non-Hodgkin lymphoma over two decades ago, a plethora of new immunotherapeutic approaches to treat lymphoma has ensued. Four of the most exciting classes of immunotherapies include: chimeric antigen receptor T-cells, bispecific antibodies, immune checkpoint inhibitors, and vaccines. However, with addition of these novel therapies the appropriate timing of treatment, optimal patient population, duration of therapy, toxicity, and cost must be considered. In this review, we describe the most-promising immunotherapeutic approaches for the treatment of lymphoma in clinical development, specifically focusing on clinical trials performed to date and strategies for improvement.

HLA class I-restricted MYD88 L265P-derived peptides as specific targets for lymphoma immunotherapy

Genome sequencing has uncovered an array of recurring somatic mutations in different non-Hodgkin lymphoma (NHL) subtypes. If affecting protein-coding regions, such mutations may yield mutation-derived peptides that may be presented by HLA class I proteins and recognized by cytotoxic T cells. A recurring somatic and oncogenic driver mutation of the Toll-like receptor adaptor protein MYD88, Leu265Pro (L265P) was identified in up to 90% of different NHL subtype patients. We therefore screened the potential of MYD88L265P-derived peptides to elicit cytotoxic T cell responses as tumor-specific neoantigens. Based on in silico predictions, we identified potential MYD88L265P-containing HLA ligands for several HLA class I restrictions. A set of HLA class I MYD88L265P-derived ligands elicited specific cytotoxic T cell responses for HLA-B*07 and -B*15. These data highlight the potential of MYD88L265P mutation-specific peptide-based immunotherapy as a novel personalized treatment approach for patients with MYD88L265P+ NHLs that may complement pharmacological approaches targeting oncogenic MyD88 L265P signaling.

Clinical Safety and Immunogenicity of Tumor-Targeted, Plant-Made Id-KLH Conjugate Vaccines for Follicular Lymphoma

We report the first evaluation of plant-made conjugate vaccines for targeted treatment of B-cell follicular lymphoma (FL) in a Phase I safety and immunogenicity clinical study. Each recombinant personalized immunogen consisted of a tumor-derived, plant-produced idiotypic antibody (Ab) hybrid comprising the hypervariable regions of the tumor-associated light and heavy Ab chains, genetically grafted onto a common human IgG1 scaffold. Each immunogen was produced in Nicotiana benthamiana plants using twin magnICON vectors expressing the light and heavy chains of the idiotypic Ab. Each purified Ab was chemically linked to the carrier protein keyhole limpet hemocyanin (KLH) to form a conjugate vaccine. The vaccines were administered to FL patients over a series of ≥6 subcutaneous injections in conjunction with the adjuvant Leukine (GM-CSF). The 27 patients enrolled in the study had previously received non-anti-CD20 cytoreductive therapy followed by ≥4 months of immune recovery prior to first vaccination. Of 11 patients who became evaluable at study conclusion, 82% (9/11) displayed a vaccine-induced, idiotype-specific cellular and/or humoral immune response. No patients showed serious adverse events (SAE) related to vaccination. The fully scalable plant-based manufacturing process yields safe and immunogenic personalized FL vaccines that can be produced within weeks of obtaining patient biopsies.

Lymphoma Immunotherapy: Current Status

The rationale to treat lymphomas with immunotherapy comes from long-standing evidence on their distinctive immune responsiveness. Indolent B-cell non-Hodgkin lymphomas, in particular, establish key interactions with the immune microenvironment to ensure prosurvival signals and prevent antitumor immune activation. However, reports of spontaneous regressions indicate that, under certain circumstances, patients develop therapeutic antitumor immunity. Several immunotherapeutic approaches have been thus developed to boost these effects in all patients. To date, targeting CD20 on malignant B cells with the antibody rituximab has been the most clinically effective strategy. However, relapse and resistance prevent to cure approximately half of B-NHL patients, underscoring the need of more effective therapies. The recognition of B-cell receptor variable regions as B-NHL unique antigens promoted the development of specific vaccines to immunize patients against their own tumor. Despite initial promising results, this strategy has not yet demonstrated a sufficient clinical benefit to reach the regulatory approval. Several novel agents are now available to stimulate immune effector functions or counteract immunosuppressive mechanisms, such as engineered antitumor T cells, co-stimulatory receptor agonist, and immune checkpoint-blocking antibodies. Thus, multiple elements can now be exploited in more effective combinations to break the barriers for the induction of anti-lymphoma immunity.

Vaccination strategies in lymphoproliferative disorders: Failures and successes

Anti-tumor vaccines in lymphoproliferative disorders hold out the prospect of effective tumor therapies with minimal side effects. The addition of immunotherapy to old and new chemotherapy regimens has improved both response rates and disease-free survival, leading in many cases to an extended overall survival. Ideally, an antigen that is used for vaccination would be specifically expressed in the tumor; it must have an important, causal part in the multifactorial process that leads to cancer, and it must be expressed stably even after it is attacked by the immune system. Immunotherapies, which aim to activate the immune system to kill cancer cells, include strategies to increase the frequency or potency of antitumor T cells, to overcome suppressive factors in the tumor microenvironment, and to reduce T-cell suppression systemically. In this review, we focus on the results of clinical trials of vaccination in lymphoma, and discuss potential strategies to enhance the efficacy of immunotherapy in the future.

Towards an off-the-shelf vaccine therapy targeting shared B-cell tumor idiotypes

The ideal tumor antigen is one expressed selectively by the tumor, present in all cancer patients, essential for tumor survival and nonetheless able to induce both humoral and cellular immune response. The personalized idiotype (Id) of the surface immunoglobulin is a tumor specific antigen in that it is expressed on clonal B-cell tumors, mediates B-cell survival, and induces tumor specific immunity in both human and animal models. With the availability of monoclonal antibodies against B cells, such as rituximab, the cellular immune response mediated by specific T cells has gained more importance as a combination therapy for the complete elimination of residual tumor cells in lymphoma and myeloma.

Structural basis for the recognition in an idiotype-anti-idiotype antibody complex related to celiac disease

Anti-idiotype antibodies have potential therapeutic applications in many fields, including autoimmune diseases. Herein we report the isolation and characterization of AIM2, an anti-idiotype antibody elicited in a mouse model upon expression of the celiac disease-specific autoantibody MB2.8 (directed against the main disease autoantigen type 2 transglutaminase, TG2). To characterize the interaction between the two antibodies, a 3D model of the MB2.8-AIM2 complex has been obtained by molecular docking. Analysis and selection of the different obtained docking solutions was based on the conservation within them of the inter-residue contacts. The selected model is very well representative of the different solutions found and its stability is confirmed by molecular dynamics simulations. Furthermore, the binding mode it adopts is very similar to that observed in most of the experimental structures available for idiotype-anti-idiotype antibody complexes. In the obtained model, AIM2 is directed against the MB2.8 CDR region, especially on its variable light chain. This makes the concurrent formation of the MB2.8-AIM2 complex and of the MB2.8-TG2 complex incompatible, thus explaining the experimentally observed inhibitory effect on the MB2.8 binding to TG2.

Targeted DNA vaccines eliciting crossreactive anti-idiotypic antibody responses against human B cell malignancies in mice

BACKGROUND

Therapeutic idiotypic (Id) vaccination is an experimental treatment for selected B cell malignancies. A broader use of Id-based vaccination, however, is hampered by the complexity and costs due to the individualized production of protein vaccines. These limitations may be overcome by targeted DNA vaccines encoding stereotyped immunoglobulin V regions of B cell malignancies. We have here investigated whether such vaccines might elicit cross-reactive immune responses thus offering the possibility to immunize subsets of patients with the same vaccine.

METHODS

Fusion vaccines targeting patient Id to mouse Major Histocompatibility Complex (MHC) class II molecules (chimeric mouse/human) or chemokine receptors (fully human) on antigen-presenting cells (APC) were genetically constructed for two Chronic Lymphocytic Leukemia (CLL) patients and one prototypic stereotyped B-cell receptor (BCR) commonly expressed by Hepatitis C Virus (HCV)-associated Non Hodgkin Lymphoma (NHL). The A20 murine B lymphoma cells were engineered to express prototypic HCV-associated B cell lymphoma BCR. Anti-Id antibody responses were studied against stereotyped and non-stereotyped BCRs on CLL patients' cells as well as transfected A20 cells.

RESULTS

DNA vaccination of mice with Id vaccines that target APC elicited increased amounts of antibodies specific for the patient's Id as compared with non targeted control vaccines. Anti-Id antibodies cross-reacted between CLL cells with closely related BCR. A20 cells engineered to express patients' V regions were not tumorigenic in mice, preventing tumor challenge experiments.

CONCLUSIONS

These findings provide experimental support for use of APC-targeted fusion Id DNA vaccines for the treatment of B cell lymphoma and CLL that express stereotyped BCRs.

Targeting of TLRs inhibits CD4+ regulatory T cell function and activates lymphocytes in human peripheral blood mononuclear cells

Accumulating evidence suggests elements within tumors induce exhaustion of effector T cells and infiltration of immunosuppressive regulatory T cells (Tregs), thus preventing the development of durable antitumor immunity. Therefore, the discovery of agents that simultaneously block Treg suppressive function and reinvigorate effector function of lymphocytes is key to the development of effective cancer immunotherapy. Previous studies have shown that TLR ligands (TLRLs) could modulate the function of these T cell targets; however, those studies relied on cell-free or accessory cell-based assay systems that do not accurately reflect in vivo responses. In contrast, we used a human PBMC-based proliferation assay system to simultaneously monitor the effect of TLRLs on T cells (CD4(+), CD8(+), Tregs), B cells, and NK cells, which gave different and even conflicting results. We found that the TLR7/8L:CL097 could simultaneously activate CD8(+) T cells, B cells, and NK cells plus block Treg suppression of T cells and B cells. The TLRLs TLR1/2L:Pam3CSK4, TLR5L:flagellin, TLR4L:LPS, and TLR8/7L:CL075 also blocked Treg suppression of CD4(+) or CD8(+) T cell proliferation, but not B cell proliferation. Besides CL097, TLR2L:PGN, CL075, and TLR9L:CpG-A, CpG-B, and CpG-C) were strong activators of NK cells. Importantly, we found that Pam3CSK4 could: 1) activate CD4(+) T cell proliferation, 2) inhibit the expansion of IL-10(+) naturally occurring FOXP3(+) Tregs and induction of IL-10(+) CD4(+) Tregs (IL-10-producing type 1 Treg), and 3) block naturally occurring FOXP3(+) Tregs suppressive function. Our results suggest these agents could serve as adjuvants to enhance the efficacy of current immunotherapeutic strategies in cancer patients.

Selective targeting of Toll-like receptors and OX40 inhibit regulatory T-cell function in follicular lymphoma

Immunotherapeutic strategies are promising approaches for the treatment of follicular lymphoma (FL). However, their efficacy may be limited by immunosuppressive elements in the immune system and tumor microenvironment. Therefore, strategies to reverse the effects of the immunosuppressive elements are needed. We observed that regulatory T cells (Tregs) were increased in the peripheral blood at diagnosis and persisted in high numbers after induction of clinical remission with a cyclophosphamide and doxorubicin-containing chemotherapy regimen in FL patients. High levels of peripheral blood Tregs prior to therapy were associated with decreased progression-free survival in FL patients treated with either chemotherapy or combination immunotherapy that targeted CD20 and PD-1 with monoclonal antibodies rituximab and pidilizumab, respectively. Intratumoral and peripheral blood Tregs potently suppressed autologous antitumor effector T cells in FL. However, the effects of FL Tregs could be reversed by triggering Toll-like receptors (TLR) with TLR ligands Pam3 CSK4 (TLR 1/2), flagellin (TLR 5), and CpG-B (TLR 9), and/or OX40. The TLR ligands synergized with each other as well as OX40 signaling to inhibit Tregs. Furthermore, they restored the function of FL tumor-specific effector T cells. Our results suggest that a state of tolerance exists in FL patients at diagnosis and after induction of clinical remission, and agents that activate TLRs 1/2, 5, and 9, and OX40 may serve as adjuvants to enhance the efficacy of antitumor immunotherapeutic strategies and preventive vaccines against infectious diseases in these patients.

Successes, failures and new perspectives of idiotypic vaccination for B-cell non-Hodgkin lymphomas

The idiotype of B-cell non-Hodgkin lymphomas has been intensively investigated for its proven immunogenicity as a promising cancer vaccine. Indeed, available data clearly indicate that these vaccines are able to induce tumor-specific immune responses and molecular remissions in patients with follicular lymphoma. However, only one of the three phase III trials performed so far demonstrated a prolonged disease-free survival in vaccinated patients. The observed failures have been mainly ascribed to defects in the study design and not to the limited efficacy of idiotype vaccines per se. Therefore, innovative and optimized idiotype-based vaccine formulations are being developed in order to overcome current limitations and improve the clinical benefit of this immunotherapeutic strategy. Among the most promising advances, the development of "off-the-shelf" vaccines appears of particular relevance, being potentially able to overcome the limitations related to the complex, time-consuming and expensive production of the individualized idiotypic vaccines currently used. Moreover, there is a pressing need to identify biomarkers suitable for the identification of the subset of patients who are most likely to benefit from vaccination. Recent findings also indicate that idiotypic vaccines may be safely and successfully used in additional clinical settings, including lymphoma patients after high-dose chemotherapy and autologous stem cell transplantation.

IGKV3 proteins as candidate "off-the-shelf" vaccines for kappa-light chain-restricted B-cell non-Hodgkin lymphomas

PURPOSE

An increasing set of B-cell non-Hodgkin lymphomas (B-NHL) show a biased usage of IGKV3-20 and IGKV3-15 immunoglobulin genes, a feature that could be exploited for the development of ready-to-use, broadly applicable cancer vaccines.

EXPERIMENTAL DESIGN

The immunogenic properties of clonal IGKV3-20 and IGKV3-15 proteins were analyzed with particular focus on their ability to elicit cross-reactive responses against molecularly related IGKV proteins expressed by different B-cell lymphoproliferative disorders.

RESULTS

IGK+ lymphoma patients show humoral and T-cell responses to IGKV3-20 and IGKV3-15 proteins and IGKV3-specific cytotoxic T lymphocytes (CTL) can be easily induced ex vivo. IGKV3-20-specific CTLs cross-react against different IGKV3 proteins, an effect mediated by the presence of 21 shared, sometimes promiscuous, T-cell epitopes, presented by common HLA class I allele products, thus assuring a broad HLA coverage of IGKV3-based vaccines. Many natural epitope variants are carried by IGK light chains expressed by a broad spectrum of B-NHLs and we show that IGKV3-20-specific CTLs cross-react also against several of these variant epitopes. Both humoral and CTL-specific responses were induced by KLH-conjugated IGKV3-20 protein in HLA-A2-transgenic mice and coinjection of IGKV3-20-specific CTLs with IGKV3-20+ or IGKV3-15+ lymphoma cells into SCID mice totally prevented tumor growth, thus confirming the ability of these effectors to mediate efficient and cross-reactive cytotoxic responses also in vivo.

CONCLUSIONS

These results provide the rationale to exploit IGKV3 proteins as "off-the-shelf" vaccines for a large fraction of lymphoma patients.

TCL1: a shared tumor-associated antigen for immunotherapy against B-cell lymphomas

Immunotherapy with therapeutic idiotype vaccines offers promise for treatment of B-cell malignancies. However, identification of novel immunogenic lymphoma-associated antigens that are universally expressed is necessary to overcome the barriers of patient-specific idiotype vaccines. Here, we determined whether T-cell leukemia/lymphoma 1 (TCL1) oncoprotein encoded by the TCL1 gene could be a target for immunotherapy of B-cell malignancies. We show that TCL1 mRNA and protein are selectively expressed in normal B cells but markedly hyperexpressed in multiple human B-cell lymphomas, including follicular lymphoma, chronic lymphocytic leukemia, mantle cell lymphoma, diffuse large B-cell lymphoma, and splenic marginal zone B-cell lymphoma. We demonstrated that TCL1-specific CD8(+) T cells can be generated from HLA-A*0201 (HLA-A2)(+) normal donors and identified TCL1(71-78) (LLPIMWQL) as the minimal epitope recognized by these T cells. More importantly, TCL1(71-78) peptide-specific T cells were present in the peripheral blood and tumor-infiltrating lymphocytes of lymphoma patients, could be expanded in vitro, and lysed autologous tumor cells but not normal B cells in an HLA-A2-restricted manner. Our results suggest that TCL1 is naturally processed and presented on the surface of lymphoma cells for recognition by cytotoxic T cells and can serve as a novel target for development of immunotherapeutic strategies against common B-cell lymphomas.

Immunotherapy for B-cell lymphoma: current status and prospective advances

Therapy for non-Hodgkin's lymphoma has progressed significantly over the last decades. However, the majority of patients remain incurable, and novel therapies are needed. Because immunotherapy ideally offers target selectivity, an ever increasing number of immunotherapies, both passive and active, are undergoing development. The champion of passive immunotherapy to date is the anti-CD20 monoclonal antibody rituximab that revolutionized the standard of care for lymphoma. The great success of rituximab catalyzed the development of new passive immunotherapy strategies that are currently undergoing clinical evaluation. These include improvement of rituximab efficacy, newer generation anti-CD20 antibodies, drug-conjugated and radio labeled anti-CD20 antibodies, monoclonal antibodies targeting non-CD20 lymphoma antigens, and bispecific antibodies. Active immunotherapy aims at inducing long-lasting antitumor immunity, thereby limiting the likelihood of relapse. Current clinical studies of active immunotherapy for lymphoma consist largely of vaccination and immune checkpoint blockade. A variety of protein- and cell-based vaccines are being tested in ongoing clinical studies. Recently completed phase III clinical trials of an idiotype protein vaccine suggest that the vaccine may have clinical activity in a subset of patients. Efforts to enhance the efficacy of active immunotherapy are ongoing with an emphasis on optimization of antigen delivery and presentation of vaccines and modulation of the immune system toward counteracting immunosuppression, using antibodies against immune regulatory checkpoints. This article discusses results of the various immunotherapy approaches applied to date for B-cell lymphoma and the ongoing trials to improve their effect.

Idiotype vaccines for lymphoma: Potential factors predicting the induction of immune responses

Over the last two decades, lymphoma idiotype vaccines have been the first human cancer vaccines to show striking evidence of biological and clinical efficacy on the one hand, as well as clinical benefit on the other. More recently, however, three large-scale, independent, randomized clinical trials on idiotypic vaccination have failed to achieve their main clinical endpoints for reasons likely to depend more on flaws in each clinical trial’s study design than on each vaccination strategy per se. Independently of these considerations, a major hurdle for the development of this substantially innocuous and yet potentially very effective type of treatment has been the fact that, even to date, no factors ascertainable before vaccination have been prospectively singled out as predictors of subsequently vaccine-induced, idiotype-specific immune as well as clinical responses. The aim of this review article is precisely to analyze what has been and what could be done in this respect in order to give a greater chance of success to future trials aimed at regulatory approval of idiotype vaccines.

Vaccination with patient-specific tumor-derived antigen in first remission improves disease-free survival in follicular lymphoma

PURPOSE

Vaccination with hybridoma-derived autologous tumor immunoglobulin (Ig) idiotype (Id) conjugated to keyhole limpet hemocyanin (KLH) and administered with granulocyte-monocyte colony-stimulating factor (GM-CSF) induces follicular lymphoma (FL) -specific immune responses. To determine the clinical benefit of this vaccine, we conducted a double-blind multicenter controlled phase III trial.

PATIENTS AND METHODS

Treatment-naive patients with advanced stage FL achieving complete response (CR) or CR unconfirmed (CRu) after chemotherapy were randomly assigned two to one to receive either Id vaccine (Id-KLH + GM-CSF) or control (KLH + GM-CSF). Primary efficacy end points were disease-free survival (DFS) for all randomly assigned patients and DFS for randomly assigned patients receiving at least one dose of Id vaccine or control.

RESULTS

Of 234 patients enrolled, 177 (81%) achieved CR/CRu after chemotherapy and were randomly assigned. For 177 randomly assigned patients, including 60 patients not vaccinated because of relapse (n = 55) or other reasons (n = 5), median DFS between Id-vaccine and control arms was 23.0 versus 20.6 months, respectively (hazard ratio [HR], 0.81; 95% CI, 0.56 to 1.16; P = .256). For 117 patients who received Id vaccine (n = 76) or control (n = 41), median DFS after randomization was 44.2 months for Id-vaccine arm versus 30.6 months for control arm (HR, 0.62; 95% CI, 0.39 to 0.99; P = .047) at median follow-up of 56.6 months (range, 12.6 to 89.3 months). In an unplanned subgroup analysis, median DFS was significantly prolonged for patients receiving IgM-Id (52.9 v 28.7 months; P = .001) but not IgG-Id vaccine (35.1 v 32.4 months; P = .807) compared with isotype-matched control-treated patients.

CONCLUSION

Vaccination with patient-specific hybridoma-derived Id vaccine after chemotherapy-induced CR/CRu may prolong DFS in patients with FL. Vaccine isotype may affect clinical outcome and explain differing results between this and other controlled Id-vaccine trials.

Vaccination strategies in follicular lymphoma

Follicular lymphoma is one of the most immune-responsive cancers. The clonal tumor immunoglobulin expressed on the surface of malignant B cells, termed idiotype, has been used as a tumor-specific antigen in therapeutic vaccination strategies for follicular lymphoma and other B-cell malignancies. A number of phase 1 and phase 2 clinical trials have established the safety and immunogenicity of idiotype vaccine in follicular lymphoma. Three randomized, double-blind, controlled phase 3 clinical trials have recently been completed to definitively evaluate the clinical benefit of idiotype vaccine in follicular lymphoma. This review focuses on the results of these idiotype vaccine trials and discusses potential strategies to enhance the efficacy of vaccines in the future.

Idiotype vaccines for lymphoma: proof-of-principles and clinical trial failures

The clonal immunoglobulin idiotype displayed on the surface of most malignant B cells is a patient- and tumour-specific antigen that can be used for therapeutic vaccination. Several studies have confirmed the biological efficacy of soluble protein idiotypic vaccination and two clinical trials have shown the clinical efficacy of this procedure. One study has demonstrated clinical benefit associated with idiotypic vaccination. However, three randomized clinical trials have recently failed to achieve their main end points for reasons that are probably unrelated to the vaccine. While scepticism towards this type of non-toxic medical intervention is mounting, such patient-specific treatments might yet see the light of day through better designed clinical trials.

Vaccination with autologous tumor-loaded dendritic cells induces clinical and immunologic responses in indolent B-cell lymphoma patients with relapsed and measurable disease: a pilot study

Eighteen relapsed patients with measurable indolent non-Hodgkin lymphoma (NHL) were vaccinated with dendritic cells (DCs) loaded with killed autologous tumor cells. Six patients had objective clinical responses including 3 continuous complete responses (CRs) and 3 partial responses (PRs), with a median follow up of 50.5 months. Eight patients had stable disease, whereas 4 had progressive disease. Clinical responses were significantly associated with a reduction in CD4+CD25+FOXP3+ regulatory T cells, an increase in CD3−CD56dimCD16+ natural killer (NK) cells, and maturation of lymphocytes to the effector memory stage in either postvaccination peripheral blood or tumor specimen samples. In partial responding patients, vaccination significantly boosted the IFN-γ–producing T-cell response to autologous tumor challenge. In one HLA-A*0201+ patient who achieved CR, IL-4 release by circulating T cells in response to tumor-specific IgH-encoded peptides was also documented. Immunohistochemical analysis of tumor biopsies using biotin-conjugated autologous serum samples revealed a tumor-restricted humoral response only in the postvaccination serum from responding patients. Collectively these results demonstrate that vaccination with tumor-loaded DCs may induce both T- and B-cell responses and produces clinical benefits in indolent NHL patients with measurable disease. This study is registered with the Istituto Superiore di Sanità: http://www.iss.it with protocol number 7578-PRE 21-801.