A non-isotopic probe-hybridization assay for residual DNA in biopharmaceuticals.

Although most biopharmaceuticals are highly purified, there is a theoretical concern that such recombinant products could be contaminated with oncogenic or bacterial DNA. A crucial part of the control of such biologicals is to ensure they do not contain more residual DNA than a safety limit suggested by the regulatory agency. Currently, the FDA has suggested a 100 pg per dose limit for residual DNA. DNA probes labeled with a radioisotope such as 32P have been commonly used in hybridization tests. Because of the radiation safety concern, we chose to develop a procedure for assessing DNA levels by either a dot or slot blot hybridization technique using a nonisotopic DNA probe and immuno-enzymatic detection. A minimum detectable limit (MDL) of < 10 pg DNA mg(-1) protein can be achieved. Method validation data demonstrated that the precision, reproducibility, and robustness of this approach are appropriate for quality control.

Immunochromatographic analysis of proteins. Identification, characterization and purity determination.

Antibodies specific to a protein and its structural variants were immobilized on a high-performance Protein G column. This column recognized and selectively subtracted specific molecules from a sample. When a size-exclusion column was coupled with this high-performance affinity column, a comparison between the elution profile before and after the antibody immobilization was used to study antigen components present in the sample. Various human growth hormone structural variants and aggregates were studied using this approach. The technique is simple, fast and does not involve the usage of radioactive material.

Solution stability of the monoclonal antibody-vinca alkaloid conjugate, KS1/4-DAVLB.

A 3-month solution stability study at 5 degrees C of the monoclonal antibody-vinca alkaloid conjugate KS1/4-DAVLB indicated that phosphate-buffered saline solutions at pH 4.5-5.5 had little tendency to lose vinca by hydrolysis, improved vinca stability, showed acceptable physical stability, and formed minimal amounts of soluble aggregates compared to solutions at pH 6.5-7.4. Hydrolysis and aggregation with concomitant loss of stability were accelerated at 30 degrees C throughout the pH range investigated. As determined by ELISA, the binding properties of KS1/4-DAVLB to tumor antigens were not affected by pH or temperature. A formulation suitable for initial clinical trials in cancer patients is described.

Quantification of antibodies to human growth hormone by high-performance protein G affinity chromatography with fluorescence detection.

The technique of high-performance affinity chromatography (HPAC) is applied to the quantitative determination of antibodies to human growth hormone (hGH) in serum from patients. An affinity column consisting of covalently immobilized protein G on a rigid support is used to capture the antibodies. Texas Red labeled hGH (hGH-TR) is used as a fluorescence probe for detecting the anti-hGH antibodies. Calibration curves are established by using a well-characterized monoclonal antibody to hGH (GHC101). The minimum detectable concentration (MDC) of anti-hGH antibody in serum is 250 ng/mL (this represents 10 ng of anti-hGH injected onto the protein G column). Analytical recoveries are 92-110% for seven replicates with 250-4000 ng/mL of GHC101. A precision of 15% relative standard deviation (RSD) can be achieved at the MDC. The precision is better above the detection limit. The linear dynamic range of the method is approximately 2 orders of magnitude. The total fluorescence recovery from the affinity column is greater than or equal to 96%. Sample analysis times are on the order of 20 min. The HPAC technique gives results in absolute units of concentration that correlate well with binding capacity values determined by radioimmunoassay.