A randomized study of KRAS-guided maintenance therapy with bevacizumab, erlotinib or metronomic capecitabine after first-line induction treatment of metastatic colorectal cancer: the Nordic ACT2 trial.

BACKGROUND: Maintenance treatment (mt) with bevacizumab (bev) ± erlotinib (erlo) has modest effect after induction chemotherapy in metastatic colorectal cancer (mCRC). We hypothesized the efficacy of erlo to be dependent on KRAS mutational status and investigated this by exploring mt strategies with bev ± erlo and low-dose capecitabine (cap). PATIENTS AND METHODS: Included patients had mCRC scheduled for first-line therapy, Eastern Cooperative Oncology Group (ECOG) 0-1 and no major comorbidities. Treatment with XELOX/FOLFOX or XELIRI/FOLFIRI + bev was given for 18 weeks. After induction, patients without progression were eligible for randomization to mt; KRAS wild-type (wt) patients were randomized to bev ± erlo (arms wt-BE, N = 36 versus wt-B, N = 35), KRAS mutated (mut) patients were randomized to bev or metronomic cap (arms mut-B, N = 34 versus mut-C, N = 33). Primary end point was progression-free survival (PFS) rate (PFSr) at 3 months after start of mt. A pooled analysis of KRAS wt patients from the previous ACT study was performed. RESULTS: We included 233 patients. Median age was 64 years, 62% male, 68% ECOG 0, 52% with primary tumor in situ. A total of 138 patients started mt after randomization. PFSr was 64.7% versus 63.6% in wt-B versus wt-BE, P = 1.000; and 75% versus 66.7% in mut-B versus mut-C, P = 0.579, with no significant difference in median PFS and overall survival (OS). In the pooled cohort, median PFS was 3.7 months in wt-B (N = 64) and 5.7 months in wt-BE (N = 62) (hazard ratios 1.03, 95% confidence interval 0.70-1.50, P = 0.867). The frequency of any grade 3/4 toxicities during mt was: 28%/58%/18%/15% (wt-B/wt-BE/mut-B/mut-C). CONCLUSIONS: Addition of erlo to bev as mt in KRAS wt mCRC did not significantly improve PFS or OS, but it did increase toxicity. KRAS status does not seem to influence the outcome of treatment with erlotinib. Metronomic cap warrants further investigation in mt strategies, given our explorative results. CLINICALTRIALSGOV: NCT01229813.

A randomized phase III trial on maintenance treatment with bevacizumab alone or in combination with erlotinib after chemotherapy and bevacizumab in metastatic colorectal cancer: the Nordic ACT Trial.

BACKGROUND: The main objective was to study the effect on progression-free survival (PFS) of adding erlotinib to bevacizumab as maintenance treatment following chemotherapy and bevacizumab as first-line treatment of metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: Patients with untreated mCRC received doublet chemotherapy + bevacizumab during 18 weeks and those without tumor progression were eligible for randomization to bevacizumab + erlotinib (arm A) or bevacizumab alone (arm B), until progression or unacceptable toxic effect. RESULTS: Of the 249 patients enrolled, 80 started maintenance treatment in arm A and 79 in arm B. The rate of any grade 3/4 toxic effect was 53% in arm A and 13% in arm B. Median PFS was 5.7 months in arm A and 4.2 months in arm B (HR = 0.79; 95% confidence interval 0.55-1.12; P = 0.19). Overall survival (OS) from start of induction chemotherapy was 26.7 months in the randomized population, with no difference between the two arms. CONCLUSIONS: The addition of erlotinib to bevacizumab as maintenance treatment after first-line chemotherapy in mCRC did not improve PFS significantly. On-going clinical and translational studies focus on identifying subgroups of patients that may benefit from erlotinib in the maintenance setting. CLINICAL TRIALS NUMBER: NCT00598156.

The value of post-operative chemotherapy after chemoradiotherapy in patients with high-risk locally advanced rectal cancer-results from the RAPIDO trial.

BACKGROUND: Pre-operative chemoradiotherapy (CRT) rather than radiotherapy (RT) has resulted in fewer locoregional recurrences (LRRs), but no decrease in distant metastasis (DM) rate for patients with locally advanced rectal cancer (LARC). In many countries, patients receive post-operative chemotherapy (pCT) to improve oncological outcomes. We investigated the value of pCT after pre-operative CRT in the RAPIDO trial. PATIENTS AND METHODS: Patients were randomised between experimental (short-course RT, chemotherapy and surgery) and standard-of-care treatment (CRT, surgery and pCT depending on hospital policy). In this substudy, we compared curatively resected patients from the standard-of-care group who received pCT (pCT+ group) with those who did not (pCT- group). Subsequently, patients from the pCT+ group who received at least 75% of the prescribed chemotherapy cycles (pCT ≥75% group) were compared with patients who did not receive pCT (pCT-/- group). By propensity score stratification (PSS), we adjusted for the following unbalanced confounders: age, clinical extramural vascular invasion, distance to the anal verge, ypT stage, ypN stage, residual tumour, serious adverse event (SAE) and/or readmission within 6 weeks after surgery and SAE related to pre-operative CRT. Cumulative probability of disease-free survival (DFS), DM, LRR and overall survival (OS) was analysed by Cox regression. RESULTS: In total, 396/452 patients had a curative resection. The number of patients in the pCT+, pCT >75%, pCT- and pCT-/- groups was 184, 112, 154 and 149, respectively. The PSS-adjusted analyses for all endpoints demonstrated hazard ratios between approximately 0.7 and 0.8 (pCT+ versus pCT-), and 0.5 and 0.8 (pCT ≥75% versus pCT-/-). However, all 95% confidence intervals included 1. CONCLUSIONS: These data suggest a benefit of pCT after pre-operative CRT for patients with high-risk LARC, with approximately 20%-25% improvement in DFS and OS and 20%-25% risk reductions in DM and LRR. Compliance with pCT additionally reduces or improves all endpoints by 10%-20%. However, differences are not statistically significant.

Continuation of fluoropyrimidine treatment with S-1 after cardiotoxicity on capecitabine- or 5-fluorouracil-based therapy in patients with solid tumours: a multicentre retrospective observational cohort study.

BACKGROUND: Capecitabine- or 5-fluorouracil (5-FU)-based chemotherapy is widely used in many solid tumours, but is associated with cardiotoxicity. S-1 is a fluoropyrimidine with low rates of cardiotoxicity, but evidence regarding the safety of switching to S-1 after 5-FU- or capecitabine-associated cardiotoxicity is scarce. PATIENTS AND METHODS: This retrospective study (NCT04260269) was conducted at 13 centres in 6 countries. The primary endpoint was recurrence of cardiotoxicity after switch to S-1-based treatment due to 5-FU- or capecitabine-related cardiotoxicity: clinically meaningful if the upper boundary of the 95% confidence interval (CI; by competing risk) is not including 15%. Secondary endpoints included cardiac risk factors, diagnostic work-up, treatments, outcomes, and timelines of cardiotoxicity. RESULTS: Per protocol, 200 patients, treated between 2011 and 2020 [median age 66 years (range 19-86); 118 (59%) males], were included. Treatment intent was curative in 145 (73%). Initial cardiotoxicity was due to capecitabine (n = 170), continuous infusion 5-FU (n = 22), or bolus 5-FU (n = 8), which was administered in combination with other chemotherapy, targeted agents, or radiotherapy in 133 patients. Previous cardiovascular comorbidities were present in 99 (50%) patients. Cardiotoxic events (n = 228/200) included chest pain (n = 125), coronary syndrome/infarction (n = 69), arrhythmia (n = 22), heart failure/cardiomyopathy (n = 7), cardiac arrest (n = 4), and malignant hypertension (n = 1). Cardiotoxicity was severe or life-threatening in 112 (56%) patients and led to permanent capecitabine/5-FU discontinuation in 192 (96%). After switch to S-1, recurrent cardiotoxicity was observed in eight (4%) patients (95% CI 2.02-7.89, primary endpoint met). Events were limited to grade 1-2 and occurred at a median of 16 days (interquartile range 7-67) from therapy switch. Baseline ischemic heart disease was a risk factor for recurrent cardiotoxicity (odds ratio 6.18, 95% CI 1.36-28.11). CONCLUSION: Switching to S-1-based therapy is safe and feasible after development of cardiotoxicity on 5-FU- or capecitabine-based therapy and allows patients to continue their pivotal fluoropyrimidine-based treatment.

A window of opportunity phase II study of enzastaurin in chemonaive patients with asymptomatic metastatic colorectal cancer.

BACKGROUND: Preclinically, protein kinase C and AKT activation can be inhibited by enzastaurin and reduce tumor growth of colorectal cancer cells. In asymptomatic patients with metastatic colorectal cancer (mCRC), enzastaurin activity was evaluated by measuring the 6-month progression-free survival (PFS) rate in a window study design. PATIENTS AND METHODS: Chemonaive patients with asymptomatic mCRC who did not require immediate chemotherapy-induced tumor reduction received a 400-mg thrice daily loading dose of enzastaurin on day 1 of cycle 1, followed by 500 mg once daily for the remaining 28-day cycles. Progression was assessed on the basis of radiographic imaging, rise in carcinoembryonic antigen or lactate dehydrogenase (LDH) levels or by appearance of clinical symptoms. RESULTS: Twenty-eight patients received daily enzastaurin. The 6-month PFS rate was 28% [95% confidence interval (CI) 13%-45%] and median PFS was 1.9 months (95% CI 1.8-4.5 months). Twelve (43%) patients had stable disease with a median duration of 6.1 months. The survival rate at 20 months was 77% (95% CI 47%-92%). No grade 4 toxicity was reported and grade 3 toxic effects were observed in three patients with one patient showing probable drug-related elevation of liver transaminases. CONCLUSION: The window design in asymptomatic patients with mCRC can be safely applied to assess the activity and safety of novel cytostatic agents like enzastaurin.

Early prediction of response to first-line chemotherapy by sequential [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography in patients with advanced colorectal cancer.

BACKGROUND: To evaluate [(18)F]-2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET), for early evaluation of response to palliative chemotherapy and for prediction of long-term outcome, in patients with metastatic colorectal cancer (mCRC). PATIENTS AND METHODS: In a randomized trial, patients with mCRC received irinotecan-based combination chemotherapy. FDG-PET was carried out before treatment and after two cycles in 51 patients at two centers. Visual changes in tumor FDG uptake and changes measured semi-automatically, as standard uptake values (SUVs), were compared with radiological response after four and eight cycles. RESULTS: The mean baseline SUV for all tumor lesions per patient was higher in nonresponders than in responders (mean 7.4 versus 5.6, P = 0.02). There was a strong correlation between metabolic response (changes in SUV) and objective response (r = 0.57, P = 0.00001), with a sensitivity of 77% and a specificity of 76%. There was no significant correlation between metabolic response and time to progression (P = 0.5) or overall survival (P = 0.1). CONCLUSIONS: Although metabolic response assessed by FDG-PET reflects radiological tumor volume changes, the sensitivity and specificity are too low to support the routine use of PET in mCRC. Furthermore, PET failed to reflect long-term outcome and can, thus, not be used as surrogate end point for hard endpoint benefit.

Quality of life and cost effectiveness in a randomized trial of patients with colorectal cancer and peritoneal metastases.

BACKGROUND: The aim was to compare health-related quality-of-life (HRQOL) and cost-effectiveness between cytoreductive surgery with intraperitoneal chemotherapy (CRS + IPC) and systemic chemotherapy for patients with colorectal peritoneal metastases. METHODS: Patients included in the Swedish Peritoneal Trial comparing CRS + IPC and systemic chemotherapy completed the EORTC QLQ-C30 and SF-36 questionnaires at baseline, 2, 4, 6, 12, 18, and 24 months. HRQOL at 24 months was the primary endpoint. EORTC sum score, SF-36 physical and mental component scores at 24 months were calculated and compared for each arm and then referenced against general population values. Two quality-adjusted life-year (QALY) indices were applied (EORTC-8D and SF-6D) and an incremental cost-effectiveness ratio (ICER) per QALY gained was calculated. A projected life-time ICER per QALY gained was calculated using predicted survival according to Swedish population statistics. RESULTS: No statistical differences in HRQOL between the arms were noted at 24 months. Descriptively, survivors in the surgery arm had higher summary scores than the general population at 24 months, whereas survivors in the chemotherapy arm had lower scores. The projected life-time QALY benefit was 3.8 QALYs in favor of the surgery arm (p=0.06) with an ICER per QALY gained at 310,000 SEK (EORTC-8D) or 362,000 SEK (SF-6D) corresponding to 26,700-31,200 GBP. CONCLUSION: The HRQOL in patients with colorectal peritoneal metastases undergoing CRS + IPC appear similar to those receiving systemic chemotherapy. Two-year survivors in the CRS + IPC arm have comparable HRQOL to a general population reference. The treatment is cost-effective according to NICE guidelines.

Pharmacokinetics of the mouse monoclonal antibody 17-1A in cancer patients receiving various treatment schedules.

Twenty-four patients with metastatic colorectal carcinoma were treated with repeated doses (200-500 mg) of the mouse monoclonal antibody (MAb) 17-1A. Four different treatment schedules were used. The total dose was 1, 3.6, 7.6, and 12 g, respectively. Altogether, 263 infusions were administered. The interindividual variations in the maximum serum concentration at 2 h (max2 h) were large. The mean max2 h value after an infusion of 200 mg was 55 +/- 5 micrograms/ml and after 500 mg, 132 +/- 7 micrograms/ml. Max2 h concentration correlated inversely with the half-life of MAb 17-1A (P less than 0.001). The t1/2 beta for 200 mg was 25.9 +/- 1.4 h and after the administration of 500 mg, 19.8 +/- 1.0 h. The total area under the concentration versus time curve increased when high doses were administered on a continuous basis, in comparison with spaced infusions, thus increasing the exposure of the tumor tissues to MAb 17-1A. The pharmacokinetics of mouse MAb 17-1A are best described by a one-compartment model. All patients developed anti-mouse IgG antibodies and most also IgM antibodies. In the more intensive treatment schedules, the IgG antibody response was suppressed. Induction of high titers of anti-mouse antibodies did not cause clinical problems. Neither did they affect the pharmacokinetics of MAb 17-1A at these dose levels. Therapy was tolerated well. The side effects were mild and of short duration. The gastrointestinal adverse reactions were dose dependent and correlated to serum max2 h concentration. Allergic reactions were rare and easily clinically manageable.

Tumor regression in monoclonal antibody-treated patients correlates with the presence of anti-idiotype-reactive T lymphocytes.

Treatment of cancer patients with unconjugated mAbs directed against tumor-associated antigens is considered passive immunotherapy due to the main suggested effector mechanisms: antibody-dependent cellular cytotoxicity, complement-dependent cytolysis, and apoptosis. The therapeutic antibody (ab1) may, however, also give rise to an idiotypic network response, i.e., an immunizing effect. Induced anti-idiotypic antibodies (ab2) mimicking the epitope that ab1 recognizes might subsequently induce an anti-anti-idiotypic humoral (ab3) and T-cell (T3) response recognizing the nominal tumor-associated antigen. Twenty-four patients with metastatic colorectal carcinoma were treated with MAb17-1A against the tumor associated antigen GA733-2 and were analyzed for the induction of T3 cells. Five of the patients responded to mAb therapy with tumor regression. These five patients all had T cells specifically recognizing human ab2 (DNA synthesis) after treatment, while all nonresponding patients lacked such T cells. Four of the five patients with ab2-reactive T cells also showed induction of T cells recognizing GA733-2. The association between T3 cells and tumor regression was highly significant (P = 0.0005). Thus, induction of T3 cells might be an important secondary antitumor effector function of therapy with unconjugated mAbs. Antibody therapy may therefore also be considered active specific immunotherapy.

Mutation screening in the hMLH1 gene in Swedish hereditary nonpolyposis colon cancer families.

Hereditary nonpolyposis colorectal cancer is caused by heritable defects in the DNA mismatch repair genes hMLH1, hMSH2, hPMS1, and hPMS2. We have used denaturing gradient gel electrophoresis to analyze the 19 exons and exon-intron borders of hMLH1 in 39 Swedish hereditary nonpolyposis colorectal cancer families. Germline mutations were found in eight of these families: two splice mutations affecting exons 3 and 7, respectively, and six missense mutations, of which, four were in exon 2 and one each were in exons 1 and 16. The relatively high number of missense mutations raises several important clinical and technical issues. Such alterations can be identified only when using methods that target DNA or mRNA sequence alteration because they do not cause protein truncations detected by in vitro translation assays. Furthermore, the relationship between these missense mutations and the predisposition to colon cancer is difficult to determine without additional information; thus, genetic counseling based on mutation data is difficult.

Cytoreductive surgery and intraperitoneal chemotherapy versus systemic chemotherapy for colorectal peritoneal metastases: A randomised trial.

BACKGROUND: First-line treatment of isolated resectable colorectal peritoneal metastases remains unclear. This study (the Swedish peritoneal study) compares cytoreductive surgery and intraperitoneal chemotherapy (surgery arm) with systemic chemotherapy (chemotherapy arm). METHODS: Patients deemed resectable preoperatively were randomised to surgery and intraperitoneal 5-fluorouracil 550 mg/m(2)/d for 6 d with repeated courses every month or to systemic oxaliplatin and 5-fluorouracil regimen every second week. Both treatments continued for 6 months. Primary end-point was overall survival (OS) and secondary end-points were progression-free survival (PFS), and morbidity. RESULTS: The study terminated prematurely when 48 eligible patients (24/arm) were included due to recruitment difficulties. Two-year OS was 54% in the surgery arm and 38% in the chemotherapy arm (p = 0.04). After 5 years, 8 versus 1 patient were alive, respectively (p = 0.02). Median OS was 25 months versus 18 months, respectively, hazard ratio 0.51 (95% confidence interval: 0.27-0.96, p = 0.04). PFS in the surgery arm was 12 months versus 11 months in the chemotherapy arm (p = 0.16) with 17% versus 0% 5-year PFS. Grade III-IV morbidity was seen in 42% and 50% of the patients, respectively. No mortalities. CONCLUSIONS: Cytoreductive surgery with intraperitoneal chemotherapy may be superior to systemic oxaliplatin-based treatment of colorectal cancer with resectable isolated peritoneal metastases.(ClinicalTrials.gov nr:NCT01524094).

Immunopathology of metastases in patients of colorectal carcinoma treated with monoclonal antibody 17-1A and granulocyte macrophage colony-stimulating factor.

Twenty patients with metastatic colorectal carcinoma were treated with a single infusion (400 mg) of a mouse monoclonal antibody (IgG2a) against the tumor-associated antigen CO 17-1A and with a daily injection of granulocyte macrophage colony-stimulating factor (GM-CSF) for 10 days. The cycle was repeated every month. Metastases from 5 of the 20 patients biopsied on days 1 and 10 of the first two treatment cycles were studied by immunohistochemistry. During treatment, neutrophils, monocytes, and T lymphocytes increased concordantly in the tumor as in the blood of the individual patient. Macrophages (CD68) and CD8+ T cells infiltrated the tumor glands and displayed TIA-1-reactive cytotoxic granules. Neutrophils were seen mainly in areas of necrosis. Activated (HLA-DR+) CD4+ T cells were usually abundant in the stroma. During treatment, few natural killer cells were found in the tumor, contrary to the marked increase seen in blood. Our observations indicate that GM-CSF markedly recruited activated, tumor-infiltrating leukocytes, possibly representing antibody-dependent cellular cytotoxicity and cytotoxic T effector cells. The notion that combined antibody and GM-CSF therapy may also promote a T-cell antitumor response is further supported and advocated by our findings. The study lends further support to combining GM-CSF with monoclonal antibody-based therapy.

Phase I study of UFT plus leucovorin with radiotherapy in patients with inextirpable non-rectal gastrointestinal cancer.

BACKGROUND AND PURPOSE: Chemoradiotherapy is increasingly used in the primary management of patients with loco-regionally advanced gastrointestinal (GI) cancer. Oral chemotherapy with uracil and tegafur (UFT) plus leucovorin (LV) may represent a convenient way of delivering protracted infusion of fluorouracil. Our goal was to evaluate the safety of UFT plus LV combined with radiation and determine the maximum-tolerated dose (MTD) and a recommended dose for further testing. PATIENTS AND METHODS: Patients with inextirpable GI cancer received escalating doses of UFT (starting at 300 mg/m(2)/d with 50 mg/m(2)/d increments between consecutive cohorts) and fixed doses of LV (90 mg/d). UFT and LV were given 5 days per week concurrently with radiation to 50 Gy (2 Gy/fraction). RESULTS: Twenty-five patients were treated, and 22 received the planned treatment. Three patients were withdrawn from treatment, two due to disease-progression and one due to toxicity. The MTD of UFT with radiation was 400 mg/m(2)/d with 90 mg/d of LV. Diarrhoea was the main dose limiting toxicity (DLT). Since some toxicity (3/12 DLTs) was seen in the expanded cohort at the level below, but none (0/9 DLT) at the starting level, the recommended dose chosen for further testing is 300-350 mg/m(2)/d depending upon the size of the target volume. CONCLUSION: Concomitant chemoradiation with oral UFT plus LV is feasible and well tolerated and should be further investigated since tumour responses were frequently seen.

Ga733/EpCAM as a target for passive and active specific immunotherapy in patients with colorectal carcinoma.

GA733/EpCAM is an oncofetal antigen abundantly expressed in colorectal carcinoma. This antigen can spontaneously induce a humoral and cellular antitumor immunity and may therefore be a suitable target structure for immunotherapy. Patients with advanced colorectal carcinoma have been treated with monoclonal antibodies (MAb17-1A) against this structure. The data indicate that the chimeric variant was not superior to the original mouse MAb. Addition of cytokines and chemotherapeutics may improve the therapeutic effect of the MAb. A particularly interesting regimen is a combination of MAb17-1A/GM-CSF/alpha-IFN/5-Fu. The GA733 protein antigen can also be used as a vaccine. Patients with colorectal carcinoma stages B and C were vaccinated with this protein antigen in combination with GM-CSF as an adjuvant cytokine. A strong type I T cell response was induced that seemed to be MHC class I as well as class II restricted. No systemic side effects were noted.

Clinical status of monoclonal antibodies in the treatment of colorectal carcinoma.

MoABs have demonstrated an antitumor effect and, in time, may lead to improved outcome in patients with colorectal cancer. The authors describe their experience in Sweden and summarize the results of other studies. Primarily, unconjugated mouse MoABs have been used--directed against tumor-associated antigens. More promising are hybrid antibodies composed of mouse and human elements (chimeric), or human MoABs. Such antibodies also can be used as carriers of a cytotoxic compound. The authors discuss two mechanisms by which MoABs induce their antitumor effect, and how cytokines combined with a MoAB can contribute to lysis. The potential roles of anti-idiotypic antibodies are outlined and the use of MoABs postoperatively is proposed.

Isolation and characterization of autologous blood mononuclear cells used for auto-infusion together with monoclonal antibodies in tumor treatment.

CO17-1A is a tumor associated antigen on colorectal carcinoma cells. A mouse monoclonal antibody of subclass IgG2A (MAb 17-1A) has been previously produced against the antigen for therapy. In a phase II study in patients with metastasizing colorectal carcinomas, leukapheresis was performed and isolated cells armed in vitro with MAb 17-1A. The mixture of MAb 17-1A and cells were infused into the patients. The aim of this procedure was to increase the number of cytotoxic cells in the tumor lesion. Two cell purification techniques (A and B) using an IBM 2991 Blood Cell Processor are described. Procedure B gave the highest yield of mononuclear cells (7.52 x 10(9) vs 5.17 x 10(9), p less than 0.01) as well as significantly higher total numbers of monocytes and NK cells. The relative ADCC activity of the two cell isolates were similar. A positive correlation between the frequency of Leu-M5+ cells (monocytes) and 51Cr release was observed. Increasing amounts of OKM1+ (CD11) cells suppressed ADCC. 35-40% of the cells bound MAb 17-1A after 1h incubation at room temperature. There was no substantial increase in cells binding MAb 17-1A upon further incubation. A strong positive correlation between the numbers of monocytes and cells binding MAb 17-1A was seen but also B lymphocytes, T lymphocytes and NK cells bound MAb 17-1A. More than 97% of the added MAb was unbound.

Effect of human blood mononuclear cell populations in antibody dependent cellular cytotoxicity (ADCC) using two murine (CO17-1A and Br55-2) and one chimeric (17-1A) monoclonal antibodies against a human colorectal carcinoma cell line (SW948).

Peripheral blood mononuclear cells (PBMC) from healthy individuals were studied for their lytic capability in ADCC using SW948 (a human colorectal carcinoma cell line) as target cells. Three monoclonal antibodies (MAbs) were used: two mouse MAbs (IgG2A) against the antigenic structures CO17-1A and BR55-2 respectively and one chimeric MAb 17-1A (IgG1) (mouse-human). Three kinds of effector cells were prepared. PBMC were purified on a Ficoll-Isopaque gradient (FIP cells) (a mixture of lymphocytes and monocytes). To obtain pure monocytes (greater than 90%), PBMC were centrifuged on a Nycodenz gradient (Nycodenz cells). Highly purified lymphocytes (greater than 98%) were obtained by treatment of FIP cells with iron powder and removal of phagocytic cells (PBL cells). Monocytes had the highest lytic capability. FIP cells were less effective than monocytes. PBL cells had the poorest killing activity. In reconstitution experiments addition of increasing amount of monocytes to PBL resulted in an augmented cytotoxicity. The numbers of Leu-M3+ cells, Leu-M5+ cells (monocytes) and CD16+ cells correlated positively to cytotoxicity. Higher concentration of MAb 17-1A was required to reach the same level of cytotoxicity using FIP cells as effector cells as compared to monocytes. MAb BR55-2 induced the same cytotoxic activity as MAb 17-1A. Combination of these two MAbs did not increase the lytic capability. Chimeric MAb 17-1A mediated ADCC in a dose-dependent fashion. The chimeric MAb was consistently more effective than the mouse MAb.

Clinical effects of monoclonal antibodies (MAb 17-1A) in patients with metastatic colorectal carcinomas.

Ten patients with metastatic colorectal carcinoma were treated with MAb 17-1A (IgG2A). Before infusion, MAb was incubated in vitro with isolated autologous blood mononuclear cells. Treatment was given in repeated courses (2-4 times) to a maximum dose of 1000 mg of MAb 17-1A. One patient achieved a clinical complete remission, two patients had a minor response and one patient had stable disease for 5 months. The median survival for the four responders was 19 months compared to 7 months for the six non-responders. Therapy was well tolerated. In this series, 32 infusions of MAb 17-1A were given. The serum half-life of MAb 17-1A was approximately 22 hours. All patients developed anti-mouse antibodies of both IgG and IgM classes. No relation between adverse reactions and anti-mouse antibodies was seen. At 3 occasions allergic reactions were noted. Skin test with MAb 17-1A seems to reliably predict for allergic reactions.

Induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies in patients treated with the mouse monoclonal antibody 17-1A (ab1). Relation to the clinical outcome--an important antitumoral effector function?

Forty-three patients with metastatic colorectal carcinoma (CRC) were treated with the unconjugated mouse monoclonal antibody (MAb) 17-1A (ab1) only. The presence of antiidiotypic antibodies (ab2) and anti-antiidiotypic antibodies (ab3) were analyzed using an ELISA technique and a mixed hemadsorption assay respectively. Ninety-five percent (41/43) of the patients developed ab2 both of the IgM and the IgG classes. Forty-seven percent (20/43) of the patients had detectable ab3 after therapy, two of them also before administration of MAb 17-1A. Binding in vitro of ab3 (ab1) to CRC cells could be specifically inhibited by ab1. Ab3 bound to human monoclonal antiidiotypic antibodies and to a goat antiidiotypic antibody (ab2). Both these ab2 were directed against MAb 17-1A (ab1). There was a strong correlation between the presence of ab3 and the clinical outcome. Ab3+ patients survived significantly longer than those who did not develop ab3 antibodies, 80 weeks vs 38 weeks (p less than 0.001). A statistically significant correlation was found between the presence of ab3 and the anti-tumor response (CR + PR + MR + SD) (p = 0.01). Thus, induction of an antiidiotypic cascade seems to be an important antitumor effector function of MAb in the treatment of cancer patients.