1. 3M Drug Delivery Systems 3 Introduction A family of hydrofluoroalkane-compatible excipients based on oligomeric lactic acid (OLA) has been proposed for use in metered does inhalers (MDIs). Because the regulatory guidances do not give specific requirements for the chemical characterization of excipients, the use of OLAs raises questions about the requirements for approval by the regulatory agencies. For this reason 3M has decided that the analytical characterization of OLA should closely mimic that of an active pharmaceutical ingredient. Oligomeric materials, such as OLA, are difficult to characterize using techniques that are commonly used in the pharmaceutical industry. Because of the random nature of the oligomerization process, OLA and associated process impurities and degradation products are not single chemical entities, but instead are mixtures of chemicals of varying numbers of repeat units (Table 1 and Figure 1). This poster describes a Normal Phase Liquid Chromatography/Atmospheric Pressure Chemical Ionization Mass Spectrometry (LC/APCI-MS) method that was developed to quantitate oligomeric process impurities and degradation products in OLA Excipient to 0.05% w/w. Kris Hansen, James Drake, Jean Osterheim, John Capecchi, Dan Dohmeier 3M Drug Delivery Systems Division, 3M Company, St. Paul, MN USA LC/MS Characterization of Oligomeric Materials Developed For Use As Excipients In Metered Dose Inhalers Experimental (cont.) Experimental SELECTIVITY ♦ How can we separate the oligomeric impurities and degradation products from the OLA Excipient? ♦ A) REVERSE PHASE CHROMATOGRAPHY  Resolves oligomers of the same compound  Insufficient resolution between different compounds Quantitation of impurities and degradation products would be difficult by RP-HPLC See Figure 2 Method Summary A) LC/MS PARAMETERS  Column: silica, 4.6 x 150 mm, 5 micron particle size, 300Å pore size  Separation mode: gradient elution, 18 minutes, Hexane/Ethyl Acetate  Mobile phase modifiers: 0.05% Formic Acid – affects peak shape and retention of analytes 1% Chloroform – electron scavenger, required for stabilization of negative corona  MS ionization: APCI  MS polarity: positive and negative  MS scan ranges: 150 – 2000 (negative), 200 – 3000 (positive) B) SAMPLE ANALYSIS  Sample: 2000 mcg/mL solution of OLA Excipient in Ethyl Acetate  Standards: 5 mcg/mL solutions of OLA Excipient (positive mode) and AcOLA-OH (negative mode)  Samples and standards are assayed in both positive and negative modes  Using known oligomer masses, Extracted Ion Chromatograms (EICs) are generated for each process impurity or degradation product  Analytes detected in positive mode are quantified using the OLA Excipient standard; analytes detected in negative mode are quantified using the AcOLA-OH standard Conclusions A Normal Phase LC/MS method has been developed for characterizing trace-level impurities and degradation products of OLA Excipient. The method can quantitate impurities to levels cited in FDA Guidance documents and has been validated to industry standards. General Structure of OLA Excipient Table 1. Impurities and Degradation Products of OLA Excipient Figure 1. Mass Spectrum of OLA Excipient and AcOLA-OH Figure 2. Example Chromatograms from the Reverse Phase LC/UV Analysis of OLA Excipient and AcOLA-OH B) NORMAL PHASE CHROMATOGRAPHY  No resolution between oligomers of the same compound  Provides resolution between OLA Excipient and some of the impurities and degradation products Normal phase chromatography alone does not provide the required selectivity See Figure 3 OLA Excipient AcOLA-OH Figure 3. Extracted Ion Chromatograms from the Normal Phase LC/MS Analysis of OLA Excipient and AcOLA-OH C) MASS SPECTROMETRY – The 2 nd Degree of Separation  Compounds that are not separated chromatographically have unique masses and can be separated and detected by mass spectrometry (MS) See Table 2 Table 2. Selectivity Matrix for OLA Excipient, Impurities, and Degradation Products ♦ Normal phase liquid chromatography coupled with detection by MS provides the selectivity and sensitivity required for quantitation of impurities and degradation products in OLA Excipient. ♦ Figure 4. Response of Individual OLA Excipient Oligomers Over Time Under Fixed LC/MS Conditions Results Method Assumptions  MS response is constant across oligomer distribution for each compound See Figure 4  Response factors for impurities and degradation products analyzed in positive mode are the same as OLA Excipient  Response factors for impurities and degradation products analyzed in negative mode are the same as AcOLA-OH With the exception of AcOLA-OH, pure standards of impurities and degradation products are very difficult to produce Figure 5. Linearity of OLA Excipient (positive mode) and AcOLA-OH (negative mode) Figure 6. Example TIC and EICs from the Analysis of OLA Excipient in Positive Polarity Mode Figure 7. Example TIC and EICs from the Analysis of OLA Excipient in Negative Polarity Mode TIC = Total Ion Chromatogram; EIC = Extracted Ion Chromatogram OLA Excipient AcOLA-OH OLA Excipient, TIC HO-OLA-R, EIC Pyr-OLA-R, EIC MC OLA, EIC OLA Excipient, TIC AcOLA-OH, EIC PyrOLA-OH, EIC METHOD VALIDATION RESULTS  Linearity: responses of OLA Excipient and AcOLA-OH highly linear (R 2 > 0.99) between 1 and 15 mcg/mL This range corresponds to impurities or degradation products present in the 2000 mcg/mL OLA Excipient sample at 0.05% to 0.75 % w/w  System precision:  5%  System drift:  10%  Method precision:  5%