[Lutetium-177-PSMA radioligand therapy : Consensus within the framework of GKV-funded care between the university hospitals in Aachen, Bonn, Düsseldorf, Essen, and Cologne and the MDK Nordrhein]. / Lutetium-177-PSMA-Radioligandentherapie : Konsensus im Rahmen der GKV-finanzierten Versorgung zwischen den Hochschulkliniken in Aachen, Bonn, Düsseldorf, Essen und Köln und dem MDK Nordrhein.

In the last 3 years, Lutetium-177 prostate-specific membrane antigen radioligand therapy (Lu-177-PSMA-RLT) has received increasing attention in nuclear medicine as a new form of treatment for castration-resistant metastatic prostate cancer. This therapy combines the radionuclide Lutetium-177, which has been therapeutically used in nuclear medicine for many years, with a molecular target of the transmembrane prostate-specific membrane antigen expressed by prostate cancer cells. Since there are no prospective randomized studies on Lu-177-PSMA-RLT and the question of reimbursement has repeatedly been the subject of review by the MDK Nordrhein (Medischenische Dienst der Krankenversicherung), there was a desire because of the increasing number of patients being treated to clarify under which circumstances Lu-177-PSMA-RLT can be reimbursed by German statutory health insurance. The goals of this article are to help treating physicians understand how this new therapy option works, to integrate it in the overall therapy concept for castration-resistant metastatic prostate cancer, and, above all, to use Lu-177-PSMA-RLT-based on the current data-at the right place in the therapy sequence of castration-resistant metastatic prostate cancer.

Apoptosis and resistance to daunorubicin in human leukemic cells.

We compared test methods based on specific mechanisms of daunorubicin (DNR) resistance to more global procedures. Assessment of P-glycoprotein (P-gp) expression and function by means of immunocytochemistry, DNR accumulation, and modulation of resistance and accumulation by the P-gp inhibitor cyclosporin A (CsA) were selected as parameters for multidrug resistance (MDR). On the other hand, we used the MTT assay and measured apoptosis and proliferative activity (S- and G2M-phases of the cell cycle) by flow cytometry. Validation of test methods was achieved for four leukemic cell lines (HL-60, KG-1a, K562/WT, K562/ADM). This battery of tests was then applied to mononuclear cells (MNC) from 18 leukemic patients. Low proficiency of MNC to undergo apoptosis and low proliferative activity rather than P-gp-mediated MDR correlated with DNR resistance as measured by the MTT assay. Bell-shaped dose-response curves for apoptosis, however, which reflect a switch from the apoptotic to the necrotic death mode with increasing cellular damage tend to limit practicability in clinical testing, because appropriate dose range and time points need to be explored. Thus, measurement of apoptosis by flow cytometry may be less convenient than the MTT assay for determination of chemosensitivity, if clinical samples with unknown patterns of responsiveness are to be tested. Spontaneous apoptosis in untreated MNC following 24 h incubation in vitro correlated significantly with DNR sensitivity in the MTT assay. A lack of essential viability factors (eg growth factors or cytokines) in vitro which are known to prevent apoptosis may contribute to DNR sensitivity.

Increased induction of apoptosis in mononuclear cells of a glucose-6-phosphate dehydrogenase deficient patient.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency belongs to the most common human disorders of metabolism. In affected patients generation of free radicals causes life-threatening hemolytic crises, for example, after consumption of certain drugs and foods or after infections. Rather than erythrocytes we analyzed mononuclear white blood cells of a patient suffering from G6PD deficiency with respect to their ability to enter apoptosis after treatment with daunorubicin, ionizing radiation, or dexamethasone. The induction of apoptosis was increased in G6PD-deficient cells compared to cells from eight normal donors. In parallel, the glutathione content of mononuclear cells from the G6PD-deficient patient was significantly decreased. While in affected patients decreased life span of erythrocytes damaged by oxidative stress has long been recognized as the mechanism underlying hemolysis, peripheral leukocytes have not received similar attention. Induction of apoptosis is a relatively complex process that has been linked to cellular glutathione content. This is the first report investigating G6PD deficiency and apoptosis.

DNA damage and apoptosis in mononuclear cells from glucose-6-phosphate dehydrogenase-deficient patients (G6PD Aachen variant) after UV irradiation.

Patients affected with X chromosome-linked, hereditary glucose-6-phosphate dehydrogenase (G6PD) deficiency suffer from life-threatening hemolytic crises after intake of certain drugs or foods. G6PD deficiency is associated with low levels of reduced glutathione. We analyzed mononuclear white blood cells (MNC) of three males suffering from the German G6PD Aachen variant, four heterozygote females of this family, one G6PD-deficient male from another family coming from Iran, and six healthy male volunteers with respect to their DNA damage in two different genes (G6PD and T-cell receptor-delta) and their propensity to enter apoptosis after UV illumination (0.08-5.28 J/cm2). As determined by PCR stop assays, there was more UV-induced DNA damage in MNC of G6PD-deficient male patients than in those of healthy subjects. MNC of G6PD-deficient patients showed a higher rate of apoptosis after UV irradiation than MNC of healthy donors. MNC of heterozygote females showed intermediate rates of DNA damage and apoptosis. It is concluded that increased DNA damage may be a result of deficient detoxification of reactive oxygen species by glutathione and may ultimately account for the higher rate of apoptosis in G6PD-deficient MNC.

Pre-transplant positron emission tomography (PET) using fluorine-18-fluoro-deoxyglucose (FDG) predicts outcome in patients treated with high-dose chemotherapy and autologous stem cell transplantation for non-Hodgkin's lymphoma.

We investigated the predictive value of sequential FDG PET before and after high-dose chemotherapy (HDT) and autologous stem cell transplantation (ASCT) in 24 patients suffering from non-Hodgkin's lymphoma (NHL). FDG PET was performed at baseline, after three cycles of induction therapy, before and after HDT with ASCT. Response assessment from sequential PET scans using standardized uptake values (SUV) was available in 22 patients at the time of transplantation. Partial metabolic response (PMR) was defined as a >25% decrease of SUV between successive PET scans [corrected]. Six of seven patients who did not achieve a PMR after complete induction therapy developed lymphoma progression, while 10 of 15 patients with complete metabolic response (CMR) or PMR remained in continuous remission. Four of seven patients with less than PMR after induction therapy died vs two of 15 patients with CMR/PMR. Median progression-free and overall survival of patients with less than PMR after HDT and ASCT was 9 and 29 months, respectively. In contrast, neither conventional re-staging nor the International Prognostic Index were predictive. These data suggest that sequential quantitative PET imaging does enlarge the concept of chemosensitivity used to select patients with high-risk NHL for HDT and ASCT or to route them to alternative treatments.

Expression of apoptosis-related oncoproteins and modulation of apoptosis by caffeine in human leukemic cells.

We investigated the modulation of radio- and chemoresistance by caffeine and mechanisms of resistance in human leukemic cell lines and mononuclear cells from 18 leukemic patients. Caffeine synergistically potentiated cytotoxicity and apoptosis induced by ionizing radiation or carboplatin (CPt), but attenuated induction of apoptosis by daunorubicin (DNR) in KG-1a cells. Since caffeine released irradiated as well as DNR-treated KG-1a cells from G2M cell cycle arrest and CPt-treated cells from S-phase arrest, this release does not fully explain the different effects of caffeine. Caffeine synergistically reduced the level of the apoptosis inhibitor glutathione after irradiation or CPt treatment. In contrast, treatment with DNR plus caffeine diminished glutathione levels to a lesser extent than DNR alone. We conclude that the effect of caffeine on glutathione depletion represents a mechanism of action by which caffeine can modulate apoptosis. Caffeine increased CPt cytotoxicity in K562 cells and its doxorubicin-resistant subline (K562/ADM), but little effect was seen in HL-60 cells or mononuclear cells from leukemic patients. Multivariate cluster analysis revealed an association of CPt resistance with the expression of c-Fos, c-N-Ras, and p53 oncoproteins and with proliferative activity (S-phase of cell cycle), but not with Bcl-2 expression.

Acute myeloid leukaemia with t(8;21) associated with "occult" mastocytosis. Report of an unusual case and review of the literature.

Approximately 20% of patients with systemic mastocytosis (SM) have an associated haematological, clonal, non-mast cell lineage disease, and most exhibit an associated myelogenous neoplasm. This report describes a 48 year old man with acute myeloid leukaemia (AML) and a type t(8;21) cytogenetic abnormality. Associated bone marrow mastocytosis (a defined subtype of SM) was only detected after successful polychemotherapy in the state of bone marrow aplasia, and persisted after complete remission of AML. The diagnosis of mastocytosis was based on the demonstration of a multifocal dense mastocytic infiltrate. The atypical mast cells showed prominent spindling and an aberrant immunophenotype, with coexpression of tryptase, chymase, KIT, and CD25-which is expressed only on neoplastic (not normal) mast cells. In addition, the transforming somatic mutation D816V of the c-kit gene was detected. Re-examination of the pretherapeutic (initial) bone marrow revealed a slight diffuse increase in partially spindle shaped mast cells also exhibiting an abnormal immunophenotype, with CD25 expression, although compact mastocytic infiltrates were not detected. Because the D816V mutation was detected in the initial bone marrow specimen, strict application of three minor diagnostic criteria (spindling, CD25, D816V) enabled a diagnosis of SM-AML to be confirmed retrospectively in the initial bone marrow tissue.

Leptin contributes to the protection of human leukemic cells from cisplatinum cytoxicity.

Leptin (ob gene) and its cognate receptor (obr) are relevant for fat metabolism. Obr shares homology with the IL-6 signal transducer gp130 and is expressed in hematopoietic cells. Since cytokines and growth factors regulate both hematopoiesis and response to chemotherapy, we tested the hypothesis of whether leptin protects leukemic cells from cytotoxicity of cisplatinum. Antisense phosphorothioate oligodeoxynucleotides (ODNs) and antisense peptide nucleic acids (PNAs) complementary to the obr gene were first tested for their growth inhibitory activity in obr expressing leukemic cells. Liposome-mediated transfection of ODNs (1-2 microM) or PNAs (0.01-1 microM) inhibited growth up to 50%. Combination treatments of cisplatinum and 0.01 microM PNA reduced growth more than cisplatinum alone. Vice versa, recombinant human leptin (rhL) diminished cisplatinum-induced growth inhibition. Finally, we investigated whether rhL affects cisplatinum-induced DNA damage and repair in the housekeeping gene beta-actin by means of real time TaqMan polymerase chain reaction. RhL reduced DNA damage and increased DNA repair. The effects are, however, modest and leptin is probably not the only player in the armory of growth factors which affect drug resistance.

Damage of the kinesin heavy chain gene contributes to the antagonism of cisplatin and paclitaxel.

Paclitaxel (TAX) and cisplatin (DDP) rank among the most promising anti-neoplastic agents for the treatment of epithelial cancer. Pre-clinical and clinical data show that the cytotoxicity resulting from the combined use of TAX and DDP is governed by the order (TAX prior DDP) > (DDP prior TAX). Since this also occurs with DNA damaging agents other than DDP, damage of a sensitivity gene may be of importance. Recently, a role of kinesin heavy chain (KHC) was uncovered for the cytotoxicity of many natural drug derivatives by use of genetic suppressor elements (Gudkov et al. (1994) Proc. Natl. Acad. Sci. USA, 91, 3744-3748). We first confirmed the dependency on the order of addition for TAX and DDP in human leukemic K562 cells taking apoptotic fraction and cell growth as endpoints. We then inhibited KHC gene expression by antisense oligodeoxy-nucleotides or KHC protein function by monoclonal antibody SUK4. Both approaches led to a reduced cytotoxicity of TAX indicating that KHC may confer sensitivity to TAX. Using a PCR-stop assay, we found that DDP indeed caused dose related DNA damage in the KHC gene. There was more DNA damage in the KHC gene than in four other genes (AFP, G6PD, MDR1, TCR-delta). Increasing doses of DDP down-regulated KHC mRNA expression more than of G6PD. There may therefore be a role of KHC for the use of TAX and DDP in combination.

Induction of apoptosis, depletion of glutathione, and DNA damage by extracorporeal photochemotherapy and psoralen with exposure to UV light in vitro.

Extra corporeal photochemotherapy (ECPT) is a novel treatment for disorders caused by aberrant T lymphocytes. The effects of ECPT were investigated in mononuclear cells (MNC) of six patients suffering from either Sezary syndrome, mycosis fungoides, systemic sclerosis, pemphigus vulgaris or Hodgkin's disease. ECPT caused moderate to severe induction of apoptosis and depletion of glutathione in the MNC of two out of these six patients. The MNC were then treated with 8-methoxypsoralen (8-MOP) and UV light in vitro and analyzed for apoptosis and glutathione levels. 8-MOP and UV light induced a profile of cellular alterations that is similar to ECPT. In addition, we measured DNA damage by means of a PCR-based methodology. As exemplified by the T-cell receptor-delta and glucose-6-phosphate dehydrogenase genes, DNA damage correlated with induction of apoptosis and depletion of glutathione. It is, therefore, reasonable to propose that UV-induced glutathione depletion contributes to DNA lesions which ultimately account for the onset of apoptosis.

[Clinical value of FDG PET for therapy monitoring of malignant lymphoma--results of a retrospective study in 72 patients]. / Klinische Wertigkeit der FDG-PET zur Therapiekontrolle bei malignen Lymphomen--Ergebnisse einer retrospektiven Studie an 72 Patienten.

AIM: Of the present retrospective study was to validate the clinical value of FDG-PET for therapy control of malignant lymphoma. METHOD: 72 patients (41 non-Hodgkin lymphomas, 29 Hodgkin's disease, 2 unclassified) received static FDG-PET scans of initially involved regions (n = 53) or of the entire neck and trunk (n = 19) after therapy. CT imaging (n = 70) and serum LDH measurement (n = 64) were also performed. Results were validated either by biopsy (n = 7) or by clinical follow-up (n = 65). The predictive value of PET was analysed in relation to different prognostic factors (stage, recurrence status, number of prior therapy regimen). RESULTS: PET obtained a sensitivity of 88%, a specificity of 83% and an overall accuracy of 85% for detection of residual disease. The values for CT were 84%, 31% resp. 54%, and for serum LDH 50%, 92% and 73%. The predictive value of PET was related to the prevalence of residual disease. PET predicted complete remission in more than 90% of patients with moderate risk (stage I-III, no relapse, no more than two different therapy regimens). In high risk patients, however, the negative predictive value of PET was 50-67%. CONCLUSION: FDG-PET is more accurate than CT imaging and LDH measurement for therapy monitoring of malignant lymphoma. Therapy success can be reliably predicted in patients with moderate risk.

Prognostic significance of positron emission tomography using fluorine-18-fluorodeoxyglucose in patients treated for malignant lymphoma.

AIM: To evaluate the prognostic significance of positron emission tomography (PET) using fluorine-18-[2]-fluoro-2-deoxyglucose (FDG) in patients treated for Hodgkin's disease (HD) or non-Hodgkin's lymphoma (NHL) compared to conventional restaging (CRS). METHODS: Fifty-six patients with either HD (n = 22), high-grade NHL (n = 26) or centrocytic-centroblastic NHL (n = 8) were included. PET was performed in 41 patients for treatment reevaluation up to three months after therapy and in patients with persisting residual masses (n = 10) or suspected relapse (n = 5) four to twelve months after treatment. The scans were evaluated qualitatively and quantitatively using standardised uptake values (SUV). Progression-free survival (PFS) was estimated to assess the prognostic value of FDG PET and clinical follow-up was taken as gold standard. RESULTS: PET was positive in nineteen of 41 patients studied for treatment reevaluation. Progression was observed after a median interval of two months (range 0-15) in sixteen of 19 patients after a positive PET scan and in three of 22 patients after a negative scan (p < .001). Median duration of follow-up in progression-free patients was 21 months (range 6-72). In patients with a partial remission in CRS progression was more common in PET-positive than in PET-negative patients (5 of 7 vs. 1 of 14; p < .01) and positivity with PET was associated with poorer PFS (p < .0025). PET studies performed four to twelve months after treatment were true negative in seven, true positive in five and false-positive in three patients. SUV > 11.35 of lymphoma lesions was associated with poorer PFS than SUV < 11.35 (p < 0.025). CONCLUSION: We conclude that FDG PET after treatment of malignant lymphoma has a high prognostic value and should be recommended in patients with persistence of residual masses.

[Comparison of findings with 18-FDG PET and CT in pretherapeutic staging of malignant lymphoma]. / Vergleich der Befunde von 18-FDG-PET und CT beim prätherapeutischen Staging maligner Lymphome.

AIM: Comparison of diagnostic efficiency of FDG-PET and CT regarding localisation, histology, size and FDG-uptake of a lesion. METHODS: CT- and FDG-PET studies of 27 patients with histologically confirmed malignant lymphoma as primary disease or relapse were evaluated retrospectively. In CT lesions with a diameter (DCT) > 15 mm were regarded as positive. Focal accumulations of FDG, not explained by physiological metabolism, found by visual interpretation in iterative reconstructed PET-scans, were quantified for diameter (DPET) and corrected standardized uptake value (SUV), corrected for partial-volume-effect. Lesions were classified depending on histology and lesion quality (lymph nodes, bulks, extranodal lesions). RESULTS: CT detected 78 lesions in 26 patients, all confirmed by FDG-PET. PET localized 18 additional lesions (+23%); in high grade NHL +25%. Both methods were equally efficient in cervical lymph nodes and lung lesions, in all other regions of lymphatic nodules and in case of liver and spleen lesions PET localized more lesions. SUV was significantly higher in high-grade NHL (19.0) than in low-grade NHL and Hodgkin's disease (10.6 resp. 11.1). DCT and DPET correlated significantly (r = 0.75). CONCLUSION: Diagnostic efficiency of FDG-PET is equivalent or superior to CT in staging of malignant lymphoma before therapy. Qualitative interpretation seems sufficient for staging, quantitative analysis may add information about malignancy grade in NHL.

Positron emission tomography with 18F-FDG to detect residual disease after therapy for malignant lymphoma.

We retrospectively evaluated the use of 18F-FDG PET for assessment of residual disease in 27 patients after therapy for malignant lymphoma. The images were evaluated qualitatively and quantitatively using standardized uptake values (SUV). All findings were validated either by biopsy or by clinical follow-up and compared with corresponding CT findings. The impact of blood glucose concentration, body weight, body surface area, lesion diameter and the time between injection and imaging on the SUVs were analysed. All 15 patients with biopsy-proven residual disease or relapse during follow-up and 11 of 12 patients who remained relapse-free were correctly identified by qualitative interpretation of the PET images. A case of pneumonitis after radiotherapy/chemotherapy accounted for the only false-positive finding. Compared with CT imaging, PET had a significantly higher specificity (P < 0.01), accuracy (P < 0.05) and positive predictive value (P < 0.05). The mean and maximum SUV of the tumour lesions were positively correlated to lesion diameter (P < 0.01) and imaging time post-injection (P < 0.01). Standardized uptake values corrected for the partial volume effect and normalized to a standardized imaging time (SUVBPT) were significantly higher (P < 0.05) in high-grade than in low-grade non-Hodgkin's lymphoma. In conclusion, 18F-FDG PET may help in the identification of patients who need additional treatment after the completion of conventional therapy. Qualitative image interpretation appears sufficient for this purpose.

[An unusual etiology of erythrocytosis in a 23-year-old primiparous woman in the 22nd week of pregnancy]. / Ungewöhnliche Ursache einer Erythrozytose bei einer 23-jährigen Erstgebärenden in der 22. Schwangerschaftswoche.

CASE REPORT: A 23-year-old pregnant woman presented with erythrocytosis and a spuriously elevated HbA1c. Family history revealed that her father has been treated with phlebotomies for the last 2 years because of erythrocytosis of unknown cause. An examination of the family members demonstrated that the patient and her father were carriers of the hemoglobin (Hb) variant Hb Andrew-Minneapolis. DISCUSSION: Hb Andrew-Minneapolis belongs to a group of hemoglobin variants with a high oxygen affinity resulting in compensatory erythrocytosis. The carriers of such hemoglobin variants are usually clinically asymptomatic, exercise tolerance appears unimpaired and there is no higher incidence of cardiovascular diseases. There is no clear-cut evidence that a maternal hemoglobinopathy with high oxygen affinity is accompanied by negative consequences for the fetus or a higher abortion rate. CONCLUSION: Hemoglobinopathies with a high oxygen affinity are a rare but important differential diagnosis of polycythemia. Under these circumstances erythrocytosis has to be accepted as the primary mode of compensation and does not require treatment, as long as blood viscosity is kept within tolerable limits. An excessively elevated or lowered HbA1c without a history or symptoms of diabetes should lead to further investigations concerning the possibility of hemoglobinopathy.

Anti-Fas/Apo-1 monoclonal antibody CH-11 depletes glutathione and kills multidrug-resistant human leukemic cells.

Apoptosis is a common pathway by which cells respond to noxious insults or growth regulatory factors. Since cellular glutathione (GSH) content has long been known to govern response to antineoplastic treatment we have compared induction of apoptosis in drug sensitive (HL-60 and K562/WT) and drug resistant (KG-1a and K562/ADM) human leukemic cell lines by the monoclonal antibody CH-11 (anti-Fas/Apo-1). Fraction of apoptotic cells and cellular GSH were determined by flow cytometry. All cell lines were induced to undergo apoptosis by exposure to mAb CH-11 independent of resistance to conventional antineoplastic treatment. In conjunction with exposure to daunorubicin, vincristine, carboplatin, cytosine arabinoside, dexamethasone, or ionizing irradiation the effect of mAb CH-11 on induction of apoptosis was no more than additive. In contrast, preincubation with IFN-gamma markedly enhanced the induction of apoptosis by mAb CH-11 due to an increase of Fas-receptor expression. In each instance, GSH content decreased with increasing fraction of apoptotic cells indicating a crucial role of GSH in the apoptotic pathway.

Pneumatosis intestinalis following cytotoxic or immunosuppressive treatment.

Pneumatosis intestinalis (PI) is an uncommon condition characterized by the presence of gas within the bowel wall. We describe 5 cases of PI that occurred after cytotoxic or immunosuppressive treatment for hematological disorders. All patients were neutropenic shortly before or at the time of diagnosis of PI, but did not show specific symptoms. The diagnosis was made by conventional X-ray and confirmed by abdominal computed tomography. Since there were no signs of secondary complications such as peritonitis, ischemia, or perforation, conservative treatment with broad-spectrum antibiotics and parenteral nutrition was initiated. All patients but 1 achieved complete resolution of PI after recovery from myelosuppression. Benign pneumoperitoneum due to PI should be considered in the differential diagnosis of free intra-abdominal air after chemotherapeutic or immunosuppressive therapy. It can be managed successfully by conservative treatment in the absence of secondary complications, if there is recovery of myelopoiesis.

[Significance of immune complexes in children with severe hemophilia A in substitution treatment with factor VIII concentrates]. / Bedeutung von Immunkomplexen bei Kindern mit schwerer Hämophilie A unter Substitutionsbehandlung mit Faktor VIII-Konzentration.

Sera and EDTA-Plasma of patients with severe Haemophilia A were analysed for immune complexes and the hemolytic activity of complement in relation to Factor VIII replacement, in order to confirm or possibly exclude a relationship to allergic reactions. Immune complexes were isolated by PEG precipitation and quantitated. In addition a solid phase ELISA assay was used to detect complement-binding complexes. Total hemolytic complement activity of the classical and the alternate pathway was measured in addition to the C3 splitproduct C3d. The results obtained from 12 patients with severe Haemophilia A showed slightly increased immune complex titers, no changes of the immune complex levels during Factor VIII replacement and no alteration of the complement system following the infusions. One patient developed an allergic reaction without evidence of complement activation.

Modified pharmacokinetics of I-asparaginase from E coli by formation of specific antibodies to I-Asparaginase of different immunoglobulin classes in children with acute lymphocytic leukemia.

Twenty-four children (2-15 years old) with acute lymphocytic leukemia (ALL) were treated intravenously with 1-Asparaginase (1-Asp) isolated from E coli at a dose of 3,000 U/kg body weight four times every third day as part of a standard chemotherapy protocol. Sera of patients were obtained prior to each infusion, immediately following each infusion, and at defined intervals (2, 4, 12, 24, 36, and 48 hours postinfusion) and assayed for 1-Asp enzymatic activity.1-Asp antigen, and anti-1-Asp antibodies. Results indicate that the in-vivo elimination half-life of 1-Asp activity in patients with no demonstrable specific antibody is approximately 5.5 hours. Half-life of enzymatic activity in patients with a moderately high level of specific antibodies (pre-infusion) was prolonged (approximately 7.0 hours) in comparison to the group with no specific antibodies. In patients with very high levels of specific antibodies several infusions could not be completed because of apparent anaphylactic reactions. In-vitro studies showed that experimental immune complexes made of 1-Asp and the IgG-fraction of a rabbit-anti-1-Asp antibody under conditions of antigen excess still exhibit enzymatic activity. On the basis of this observation we conclude that specific antibodies to 1-Asp in vitro and, most likely, in vivo do not inactivate the drug but may lead to either delayed elimination of enzyme activity or, in the presence of high levels of specific antibodies, anaphylactic reaction.