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© 2003 American Society for Clinical Oncology
Fully Synthetic Carbohydrate-Based Vaccines in Biochemically Relapsed Prostate Cancer: Clinical Trial Results With
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONAUTHORS’ DISCLOSURES OF...REFERENCES |
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-N-acetylgalactosamine-O-serine/threonine (Tn), which is highly simplistic in its structure and can induce a relevant humoral response when given in a trimer or clustered (c) formation. We tested for an antitumor effect, in the form of a change in the posttreatment versus pretreatment prostate-specific antigen (PSA) slopes, that might serve as a surrogate for effectiveness of vaccines in delaying the time to radiographic progression. Methods: We compared the antibody response to immunization with two conjugates, Tn(c)-keyhole limpet hemocyanin (KLH) and Tn(c)-palmitic acid (PAM) with the saponin immunologic adjuvant QS21, in a phase I clinical trial in patients with biochemically relapsed prostate cancer. Patients received Tn(c)-KLH vaccine containing either 3, 7, or 15 µg of Tn(c) per vaccination. Ten patients received 100 µg of Tn(c)-PAM. QS21 was included in all vaccines. Five vaccinations were administered subcutaneously during 26 weeks with an additional booster vaccine at week 50.
Results: Tn(c), when given with the carrier molecule KLH and QS21, stimulated the production of high-titer immunoglobulin M (IgM) and IgG antibodies. Inferior antibody responses were seen with T(c)-PAM. There was no evidence of enhanced immunogenicity with increasing doses of vaccine. An antitumor effect in the form of a decline in posttreatment versus pretreatment PSA slopes was also observed.
Conclusion: A safe synthetic conjugate vaccine in a trimer formation was developed that can break immunologic tolerance by inducing specific humoral responses. It seemed to affect the biochemical progression of the disease as determined by a change in PSA log slope.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONAUTHORS’ DISCLOSURES OF...REFERENCES |
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-N-acetylgalactosamine-O-serine/threonine (Tn) is a monosaccharide found to be highly expressed by mucins on most epithelial cancers,1–6 with the highest expression on prostate cancer. Tn may be covalently attached to chains of serines or threonines, one sugar per amino acid, to form clusters (c) and is highly conserved. The rationale for studying epitope clustering is based on the known structure of mucins. These glycoproteins display alpha serine and threonine o-linked glycoprotein domains in a context wherein the epitopes are carried on adjacent residues in blocks and clusters.7,8 Indeed, such clusters are often the preferred targets for antitumor monoclonal antibodies in active immunity.9,10 We have previously shown that glycopeptides containing clustered sialyted (sTn) epitopes are more effective than related structures with single sTn epitopes in producing antitumor cell antibodies.11 The method used to synthesize these molecules is based on a paradigm of glycal assembly, which has been previously described.12,13 It has been proposed that the essential immunogenic structure for Tn antigen (which is intensely expressed on desialylated ovine submaxillary mucin) is a cluster of three to four consecutive monosaccharides.9 Immunization of mice with desialylated ovine submaxillary mucin or glycophorin results in high-titer antibodies against Tn and sTn respectively, and protection from tumor challenge with the Tn- and sTn-positive syngeneic breast cancer cell line, TA3-HA.14 Mice immunized with synthetic Tn(c)-keyhole limpet hemocyanin (KLH) plus the saponin immunologic adjuvant QS21 showed immunoglobulin (Ig) M and IgG titers of 1:1,350 and 1:450, respectively, after the third immunization. IgM and IgG titers increased to 1:25,600 and 1:25,600, respectively, after the fifth vaccination. In a similar study, mice immunized with Tn(c) plus tripalmitoyl-S-glycerylcysteinylserine (PAM), a potent macrophage and B-lymphocyte activator, developed median IgM and IgG titers of 1:1,350 and 1:150, respectively.15
Our studies16 with monoclonal antibody (MoAb) B72.3 and with sera raised against sTn-KLH conjugate vaccines in mice and in breast cancer patients suggested that the immune system could preferentially recognize cluster formations of these simple molecules.17,18 The availability of synthetic sTn clusters (trimers) enabled us to prove this hypothesis. In both direct tests and inhibition assays, B72.3 recognized sTn trimers and sera from mice immunized with sTn(c)-KLH reacted strongly with both natural mucins and tumor cells expressing sTn.10,18
The rationale for vaccine therapy in prostate cancer is based on several ideas: a variety of protein and carbohydrate molecules that are self-antigens are expressed on the tumor surface and may serve as targets for immune recognition and immune attack through the abrogation of tolerance; a biomarker, prostate-specific antigen (PSA), is widely available and can be used to monitor disease progression; and deferring hormonal therapy, a standard, does not compromise outcome. Our previous clinical trials with the glycoproteins mucin-1 (MUC-1) and MUC-2 and with glycolipids globo H and GM2 showed that immunization with synthetic antigens conjugated to KLH and given with QS21 had minimal toxicity and was highly immunogenic.19
We have been successful in generating a specific high-titer immune response to the immunizing molecule by designing vaccines covalently conjugated to immunogenic foreign proteins such as KLH for enhanced presentation to the immune system and using them with a potent immunologic saponin adjuvant to augment immunogenicity further (ie, with QS21). These vaccines have been administered in the adjuvant setting in which no disease or minimal disease is present and have generated specific high-titer antibodies.
We have applied these concepts to create a triple Tn cluster terminating in a sulfhydryl group, which is useful for conjugation to a carrier structure. This carrier was KLH or the more tractable and defined (and lower molecular weight) immunostimulant palmitic acid. We present the results of immunization with three different doses of Tn(c) antigen conjugated to KLH or to the B-lymphocyte activator PAM, plus QS21. In addition, we tested for an antitumor effect in the form of a change in the posttreatment versus pretreatment PSA slopes that might serve as a surrogate for effectiveness of vaccines in delaying the time to radiographic progression.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONAUTHORS’ DISCLOSURES OF...REFERENCES |
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. Tn(c) is synthesized using the glycal assembly strategy and purified as previously described.15,20 Tn(c) is conjugated to KLH using m-malemimidobenzoyl-N-hydroxysuccinamine ester (MBS), which is a heterobifunctional linker agent.19 At neutral pH, MBS crosslinks thiol groups with amino groups (Fig 1). The thiol group is provided by the mercaptoacetate linker on the Tn(c), and the amino group by the N-terminus and lysine side chains of KLH. After linkage to KLH, the MBS plus KLH conjugate is purified by column elution and cross-linked to mercaptoacetate on Tn(c). Unbound Tn(c) is removed by passage of the reaction mixture through a Centriprep 30 filter (Millipore, Billerica, MA) with a 30,000 molecular weight cutoff. The Tn(c)/carrier protein ratio in the conjugate is calculated by estimation of protein content by standard protein determination methods, and Tn(c) is calculated by the high-performance anion exchange chromatography and pulsed amperometric detection assay, which measures carbohydrate content. Aliquots of Tn(c)-KLH containing 3, 7, or 15 µg of Tn(c) are suspended in 0.6 mL of normal saline and placed in sterile 1.8-mL screw-cap plastic vials. QS21 (Antigenics, New York, NY) at 100 µg in 0.2 mL normal saline was then added to each vial just before injection. The pH of the final formulation was 6.6; the Tn(c)/KLH molar ratio was 202:1.
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). The Tn(c)-PAM vaccine comprises three separate components mixed together immediately before immunization: aliquots of Tn(c)-PAM conjugate containing 100 µg of Tn(c)-PAM are suspended in 0.4 mL of 10% dimethyl sulfoxide (vial 1). A separate vial (vial 2) contains 100 µg of QS21 suspended in 0.2 mL of normal saline. Vial 3 contains Intralipid (KabiVitrum Inc, Stockholm, Sweden). Except for the Intralipid, the other two components are stored at - 80° C. Before vaccination, the pharmacist mixes vials 1 and 2, then combines them with 0.6 mL of Intralipid. The Tn(c) dose in Tn(c)-PAM vaccines was 100 µg based on our previous studies with gangliosides, wherein a three-fold to 10-fold greater dose was required when antigens were not conjugated to immunogenic proteins.21
Patient Eligibility
Patients with biochemically relapsed prostate cancer were eligible for the study with the following restrictions: Karnofsky performance status more than 60%, WBC 
3,500/µL, platelet count 100,000/µL, bilirubin less than 2.0 mg/100 mL or AST less than 3.0 x the upper limit of normal, and serum creatinine 
2.0 mg/100 mL or creatinine clearance 40 mL/min. Patients had to have recovered from the toxicity of any therapy and could not have received chemotherapy or radiation therapy for at least 4 weeks before entry onto the trial. No history of an active secondary malignancy within the prior 5 years except for nonmelanoma skin cancer was permitted. All patients gave written informed consent.
Patients could not be enrolled if they had radiographically evident disease. Patients must have had three consecutively increasing PSA values determined at a minimal interval of 2 weeks on the basis of the following criteria: patients who had undergone prostatectomy must have had a minimal PSA entry value of 1.0 ng/mL with a 50% increase in range of values; patients who had undergone radiation therapy must have had minimal PSA entry of 2.0 ng/mL with a 50% increase in range of values. Patients with primary treatments who were receiving intermittent hormonal therapy were also permitted with no defined minimal PSA value. Patients with androgen-independent disease were excluded.
Dose and Immunization Schedule
Three sequential groups of five patients received Tn(c)-KLH vaccine containing 3, 7, and 15 µg of Tn(c) per vaccination, corresponding to treatment groups 1, 2, and 3, respectively. The fourth group included 10 patients who were treated with 100 µg of Tn(c)-PAM. In all vaccines, 100 µg of QS21 was included. Five vaccinations were administered subcutaneously to random sites on the upper arms and upper legs during weeks 1, 2, 3, 7, and 19, with an additional booster vaccine at week 50.
Serologic Assays
Serum samples were obtained at weeks 1, 2, 3, 7, 9, 13, 19, and 26. Patients were monitored expectantly on completion of the vaccine trial on a monthly basis for the first 6 months then at 3-month intervals, at which time routine blood samples were collected for both immunologic studies and biochemical markers, such as PSA and acid phosphatase. IgM and IgG antibody titers were measured by enzyme-linked immunosorbent assay (ELISA), as described previously,22,23 and IgG subclasses were determined by using IgG subclass-specific antibodies (Zymed, San Francisco, CA). Plates were read at 10 to 15 minutes for IgG and 25 to 30 minutes for IgM on an ELISA plate reader (model 550 Microplate Reader; Bio-Rad, Hercules, CA) at 414 nm. The titer was defined as the highest dilution yielding an optical density of 0.1.
Flow Cytometric Analysis
Fluorescent-activated cell sorting (FACS) was performed as previously described22 to demonstrate antibody binding to the cell surface of the cell line, LSC, a colon carcinoma cell line known to express Tn.4 Pre- and postimmunization sera were diluted two-fold to four-fold from their maximum antibody titer determined by ELISA and incubated with LSC cells for 1 hour on ice. The cells were washed, treated with goat antihuman IgM or IgG labeled with fluorescein isothiocyanate, and analyzed by flow cytometry for percent positive cells as described previously.17 MoAb IE3 served as a positive control.4
Complement-Dependent Cytotoxicity
Complement-dependent cytotoxicity was assayed on LSC and MCF7 cell lines using a 2-hour 51-chromium release assay as previously described18 with human complement and pre- and posttreatment sera at a dilution of 1:4, or with MoAb at 10 µg/mL.
Pre- and Posttherapy Evaluations
Interval safety assessments included a patient diary. Antitumor and restaging assessments with bone and computed tomography scans were performed during week 13 and then at 3-month intervals after week 26. Patients were seen monthly for the first 6 months, then every 3 to 4 months thereafter. Blood samples for immune studies were drawn at the time of each clinic visit. If the patient did not demonstrate radiographic progression of disease, the patient received a fifth vaccination on week 19 and a sixth at week 50.
Biostatistical Assessment of Treatment Effects: Change in PSA Slopes
Twenty-five patients were accrued to the trial, 15 to Tn(c)-KLH and 10 to Tn(c)-PAM, of whom all were assessable. PSA measurements were collected serially before, during, and after vaccination. For this analysis, only those PSA measurements collected within 72 weeks before vaccination were used to calculate the prevaccine log PSA slopes. The treatment period was from weeks 0 to 26. PSA measurements collected up to 50 weeks after completing the vaccination were used to calculate the postvaccine log PSA slopes. All PSA measurements collected during the initial 26-week vaccination period were excluded because of the observation that all PSAs continued to increase during the initial immunization period of 26 weeks. Percent change in log PSA slope was summarized. A 95% bootstrap-t CI24 was constructed for the percent difference in log PSA slopes between pre- and postvaccine therapy.
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RESULTS |
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Vaccine Safety Monitoring
All 25 patients completed the five immunizations. Of the 15 patients treated with Tn(c)-KLH, 14 (93%) experienced transient pain at the injection site, with 11 patients (73%) developing erythema and induration, and five patients (33%) complaining of transient grade 1 arthralgias or myalgias. Five of the 10 patients treated with Tn(c)-PAM also developed grade 1 arthralgias or myalgias and nine patients (90%) developed grade 2 local irritation. Two patients developed pruritic symptoms.
Immunologic Assessment
The median IgM antibody titers against Tn(c) by ELISA before vaccination were 1:10 or less in all four treatment groups, although the IgG ranges for dose levels at 3, 7, and 15 µg were 1:10 to 1:640, 1:10 to 1;320, and 1:20 to 1:320, respectively. IgM and IgG antibodies developed by week 3 in all Tn(c)-KLH treatment groups, and by week 7 median IgM and IgG antibody titers had reached their peak values of 1:640 (Fig 2A and 2B). One patient treated at the Tn(c)-KLH 3-µg dose level developed only IgG antibodies with peak titer of 1:5,120 by week 26; another patient at the 7-µg dose level also developed only IgG antibodies with maximum antibody titer by week 26 of 1:10,240. All others developed IgM and IgG antibodies at all dose levels of Tn(c)-KLH (Fig 2B). The antibodies persisted through week 26 and, although still detectable at week 50, had declined in most patients by at least four-fold from the maximum titers. IgG antibodies were mainly of the IgG1 and IgG3 subtype as determined by ELISA (Fig 3). All patients received a booster immunization by week 50. Antibody titers did not increase significantly with the sixth immunization. Overall, the IgM and IgG titers at the 3-µg dose were at least as high as those at the higher doses.
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FACS Reactivity of Pre- and Posttreatment Sera With LSC Cell Line
Reactivity of pretreatment and peak titer posttreatment sera was assayed by FACS against LSC cells. Pretreatment sera were gated to reactivity of 10% positive cells and compared with posttreatment reactivity. In patients vaccinated with Tn(c)-KLH, the IgM antibodies in posttreatment sera of five of 15 patients, and IgG antibodies of one additional patient, demonstrated a two-fold to nine-fold increase in the percentage of positive cells (Table 1). Only one patient vaccinated with Tn(c)-PAM showed increased posttreatment reactivity of 28% by FACS (data not shown).
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Analysis of Treatment Effect
There did not seem to be a correlation between antibody titer and time to radiographic progression of disease in bone. Within the first treatment cohort with Tn(c)-KLH-QS21 vaccine, two patients remain active and free of disease for 55 months, respectively; the remaining three patients developed disease progression within a median time of 22 months. Similarly, within the second dose level, one patient remains without disease for 55 months; three patients had a median disease progression of 14 months. Of these three, one patient experienced disease progression after 41 months; one patient discontinued follow-up because of PSA anxiety. The third dose level has two active patients at 53 months with a median disease progression in the remaining patients of 16 months, although one patient experienced disease progression in the lung after 41 months. Of the 10 patients treated with Tn(c)-PAM, three patients remain radiographically free of disease at 50 months. One patient elected to stop treatment because of PSA anxiety.
Alteration in PSA
As seen in previous studies with globo H-KLH vaccine, patients receiving both Tn(c)-KLH and Tn(c)-PAM showed slowly increasing PSA values during the first 26 weeks of the trial. One patient (patient 1; Fig 3A) treated with Tn(c)-KLH (at 3 µg) and who made high-titer IgG antibodies had a maximum PSA value of 41.9 in May 1998, which in January 1999 declined to 6.15, within 8 months of completing vaccine therapy. The PSA value remained stable in the 8 to 9 range from December 1998 through March 2000 (27 months). He remains active on the expectant monitoring phase of the trial and continues to do well for more than 55 months, with PSA values that are now starting to approach his pretreatment value. The patient has not shown any evidence of radiographic progression of disease.
Twenty-four patients treated had a minimum of three PSA measurements collected within 72 weeks before vaccination. Of the 15 patients treated with Tn(c)-KLH, one patient (patient 1) had only two PSA measurements during this time period; a third prevaccine PSA measurement was collected for this patient at approximately week 96. Twenty-three patients had a minimum of three PSA measurements between week 26 and week 50; the remaining two patients had a minimum of three PSA measurements postvaccination. Eleven patients (44%) experienced at least a 25% increase in their PSA slopes after vaccine therapy, whereas seven patients (28%) experienced at least a 25% decrease in their log PSA slopes postvaccination. Seven patients (28%) had stable disease (- 25% < percent change < 25%). Of the five patients who showed more than a 25% decline in PSA slopes after receiving the Tn(c) vaccine, three were treated at the 3-µg dose level and two were treated at the 7-µg dose level. No patient at the 15-µg dose level showed a decline in PSA log slope. Changes in two representative patients are seen in Figure 3A and 3B. Using 200 bootstrap samples, the CI has a lower boundary of -21% and an upper boundary of 328.9%.
The analysis of 15 patients treated with Tn(c)-KLH showed five patients (33%) had more than a 50% decrease in slope at 50 weeks compared with three patients (20%) who had more than a 50% increase in slope at week 50. Seven patients (46.7%) had stabilization of slopes at week 50. Of 10 patients treated with Tn(c)-PAM, one patient had more than a 50% decrease in slope at week 50, compared with three patients (30%) with more than a 50% increase at the same time sequence.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONAUTHORS’ DISCLOSURES OF...REFERENCES |
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The second component is a carrier molecule, usually an immunogenic protein—we have found KLH to be optimal in the past1—but recently, lipids such as PAM have served this purpose. KLH was identified as optimal in our early studies comparing the impact of different carrier molecules on antibody response to the glycolipids GM2 and GD3.25,26 Since then, we have used KLH conjugation plus the immunologic adjuvant QS21 to successfully induce antibodies against more than 10 different cancer-related carbohydrate and peptide antigens. KLH is a large, cumbersome molecule, and so a smaller, better-defined carrier molecule, such as PAM, would be welcome if it were equally effective as an immune potentiator. The final component is the immunologic adjuvant, the strongest of which in our experience is QS21. This trial compared the antibody response to vaccination with Tn(c)-KLH at three doses, plus the immunologic adjuvant QS21, to the response after vaccination with Tn(c)-PAM plus QS21.
Though Tn antigen monomers are expressed on a variety of normal epithelial tissues, there was no evidence of autoimmunity or other expected toxicity. This is not surprising, given that the distribution of Tn clusters is essentially exclusively restricted to cancer cells. The results establish the safety and a surprisingly low optimally immunogenic dose of the synthetic Tn(c) conjugate in patients with biochemically relapsed prostate cancer. All patients immunized with Tn(c)-KLH developed good antibody responses against Tn(c), confirming the immunogenicity of this Tn(c) vaccine. Of the three doses tested, the 3-µg dose seemed optimal, but no significant differences were observed in antibody titers with increasing doses of Tn(c)-KLH. In other vaccine trials,19 even lower doses of vaccine have been shown to be even more effective, suggesting that higher doses of vaccine may be more suppressive in inducing antibody responses. The lack of significant reactivity of sera from patients immunized with Tn(c)-KLH plus QS21 by FACS analysis has been seen previously in a variety of our earlier trials with MUC-2-19 and globo H-KLH22 conjugate vaccines. The most likely explanation is that the cell lines used for these experiments may lose expression of the various naturally occurring antigens with further in vitro passage and may not reflect the actual expression of what is naturally expressed by tumors in vivo. Assays such as antibody-dependent cell-mediated cytotoxicity and complement lysis are in vitro tests that may not represent the true level of function of the antibodies generated.
PAM is a potent B-lymphocyte and macrophage activator in murine studies. It is derived from the immunologically active N-terminal sequence of an Escherichia coli lipoprotein and has been used to augment the immunogenicity of peptides and carbohydrates.20 We have previously immunized groups of mice with Tn(c) conjugated with either KLH or PAM and administered with QS21. Tn(c)-PAM generated a comparable IgM antibody response to that generated with the KLH conjugate vaccine (median titer 1:102,500) but little or no IgG response. The Tn(c)-PAM vaccine is especially appealing because it is totally synthetic and better defined than Tn(c)-KLH, but PAM has never been used in humans. In this trial, Tn(c)-PAM was able to induce inferior IgM antibodies against Tn in most patients, compared with IgM and IgG antibody responses generated by the KLH conjugate. Cell surface reactivity by IgM FACS was restricted to one patient.
The observation of PSA slope declines over a period of several months after completion of the vaccinations has been seen in several of our other pilot trials with other antigens, and has been observed in trials with genetically altered prostate cancer cell vaccines given with cytokines such as granulocyte-macrophage colony-stimulating factor27 or fusion proteins with acid phosphatase–primed dendritic cells.28 The clinical impact of stabilization or decline of posttreatment compared with pretreatment PSA log slopes and its relevance as an intermediate end point remains to be validated. The trial described here did not address the relevance of a change in PSA value in prognosticating the clinical course in this patient population. It is important to identify patients who are at significant risk of radiographic recurrence as early as feasible and to consider these patients for investigational approaches while they still have a low tumor burden. Whether a multivalent vaccine will work better as a single modality or in combination with hormonal therapy or even chemotherapeutic regimens in high-risk patients in early relapse remains under investigation. A phase II multivalent trial for high-risk patients has been completed and is the subject of a forthcoming report by our group.
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AUTHORS’ DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONAUTHORS’ DISCLOSURES OF...REFERENCES |
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NOTES |
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REFERENCES |
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15. Kuduk SD, Schwarz JB, Chen X, et al: Synthetic and immunological studies on clustered modes of mucin related Tn and TF o-linked antigens: The preparation of glycopeptide based vaccines for clinical trials against prostate cancer. J Am Chem Soc 120:12474–12485, 1998[CrossRef]
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20. Ragupathi G, Koganty RR, Qiu DX, et al: A novel and efficient method for synthetic carbohydrate conjugate vaccine preparation: Synthesis of sialyl Tn KLH conjugate using a 4-(4-N-maleimidomethyl)cyclohexane-1-carboxyl hydrazide (MMCCH) linker arm. Glycoconj J 15:217–221, 1998[CrossRef][Medline]
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23. Ragupathi R, Slovin SF, Adluri S, et al: A fully synthetic globo H carbohydrate vaccine induces a focused humoral response to prostate cancer patients: A proof of principle. Angew Chem Int Ed 38:563–566, 1999[CrossRef]
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28. Smal EJ, Fratesi P, Reese DM, et al: Immunotherapy of hormone-refractory prostate cancer with antigen-loaded dendritic cells. J Clin Oncol 18:3894–3903, 2000
Submitted April 15, 2003; accepted September 15, 2003.
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P. J. Sabbatini, G. Ragupathi, C. Hood, C. A. Aghajanian, M. Juretzka, A. Iasonos, M. L. Hensley, M. K. Spassova, O. Ouerfelli, D. R. Spriggs, et al. Pilot Study of a Heptavalent Vaccine-Keyhole Limpet Hemocyanin Conjugate plus QS21 in Patients with Epithelial Ovarian, Fallopian Tube, or Peritoneal Cancer Clin. Cancer Res., July 15, 2007; 13(14): 4170 - 4177. [Abstract] [Full Text] [PDF]
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 P. Sabbatini and K. Odunsi Immunologic Approaches to Ovarian Cancer Treatment J. Clin. Oncol., July 10, 2007; 25(20): 2884 - 2893. [Abstract] [Full Text] [PDF]
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 H. F. Valenzuela, K. E. Pace, P. V. Cabrera, R. White, K. Porvari, H. Kaija, P. Vihko, and L. G. Baum O-Glycosylation Regulates LNCaP Prostate Cancer Cell Susceptibility to Apoptosis Induced by Galectin-1 Cancer Res., July 1, 2007; 67(13): 6155 - 6162. [Abstract] [Full Text] [PDF]
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J. W. Simons, M. A. Carducci, B. Mikhak, M. Lim, B. Biedrzycki, F. Borellini, S. M. Clift, K. M. Hege, D. G. Ando, S. Piantadosi, et al. Phase I/II Trial of an Allogeneic Cellular Immunotherapy in Hormone-Naive Prostate Cancer. Clin. Cancer Res., June 1, 2006; 12(11): 3394 - 3401. [Abstract] [Full Text] [PDF]
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T. Freire, R. Lo-Man, F. Piller, V. Piller, C. Leclerc, and S. Bay Enzymatic large-scale synthesis of MUC6-Tn glycoconjugates for antitumor vaccination Glycobiology, May 1, 2006; 16(5): 390 - 401. [Abstract] [Full Text] [PDF]
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 G. Ragupathi, N. X. Liu, C. Musselli, S. Powell, K. Lloyd, and P. O. Livingston Antibodies against Tumor Cell Glycolipids and Proteins, but Not Mucins, Mediate Complement-Dependent Cytotoxicity J. Immunol., May 1, 2005; 174(9): 5706 - 5712. [Abstract] [Full Text] [PDF]
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 S. J. Keding and S. J. Danishefsky Natural Product Synthesis Special Feature: Prospects for total synthesis: A vision for a totally synthetic vaccine targeting epithelial tumors PNAS, August 17, 2004; 101(33): 11937 - 11942. [Abstract] [Full Text] [PDF]
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Copyright © 2003 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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-N-Acetylgalactosamine-O-Serine/Threonine Conjugate Vaccine
