Human factors and usability engineering in the development of SMT-101 for the treatment of pulmonary arterial hypertension.

BACKGROUND: SMT-101, a novel, proprietary, water-resistant wearable infusion pump prefilled with a preset dosage of treprostinil, was designed to address many of the administration-related shortcomings of existing parenteral therapy for pulmonary arterial hypertension (PAH). The objective of the human factors (HF) program was to demonstrate that the SMT-101 system is safe and effective when used by patients with PAH, their caregivers, or healthcare providers. METHODS: The HF program for SMT-101 consisted of 8 studies (148 participants): an ethnographic study, an online survey of patients with PAH, 4 formative studies, a study of the instructions for use (IFU), and a summative study for validation. The pump and IFU were iteratively modified using observational data and participant feedback to inform subsequent improvements throughout the HF program to optimize safe use of SMT-101 before the final study. RESULTS: The results of the summative study demonstrated that the design of the SMT-101 wearable, pre-filled infusion pump and IFU are safe and effective for use. CONCLUSIONS: In accordance with regulatory guidelines, the usability and HF aspects of SMT-101 were developed and refined through a rigorous HF program in patients with PAH and healthcare providers, which culminated in a summative study that validated the usability and use-safety of SMT-101.

Comparison of the Pharmacokinetics of Ketorolac Tromethamine After Continuous Subcutaneous Infusion and Repeat Intramuscular Bolus Injections in Healthy Adult Subjects.

Ketorolac tromethamine is a nonsteroidal anti-inflammatory drug that exhibits analgesic activity with no sedative or anxiolytic properties. Twelve healthy male subjects were enrolled in a study to receive either of 2 treatments over 2 periods in an open-label, randomized, 2-way crossover design: (A) 120 mg of ketorolac tromethamine administered as a continuous subcutaneous infusion over a 24-hour period; or (B) an identical total daily dose administered as 4 intramuscular bolus injections of 30 mg each given every 6 hours (current labeled treatment regimen). The pharmacokinetic and safety profiles were evaluated for both treatments. Both modes of administration have similar values for area under the curve (AUC) and half-life (t1/2 ), suggesting that continuous subcutaneous infusion and repeated intramuscular bolus injections have similar bioavailability. The peak plasma concentration (Cmax ) was 40% lower when ketorolac was administered as a continuous subcutaneous infusion compared with repeat intramuscular bolus injections. The concentration at steady-state (Css ) for continuous subcutaneous infusion was between the Cmax and Ctrough values obtained following the 4 intramuscular injections. Both treatment arms were well tolerated.

In Vitro and In Vivo Performance of a Pre-Filled, Electrochemically-Actuated Infusion System.

PURPOSE: A novel infusion system (PatchPump®) has been developed using an electrochemical actuator and a semi-flexible container to deliver liquid formulations through an infusion set. In vitro studies characterized pump performance, and clinical studies evaluated functionality and pharmacokinetic (PK) performance in humans. METHODS: Total delivered volume and flow rate accuracy were determined in vitro by real-time gravimetric analysis. Functionality was evaluated in vivo using prototype devices delivering saline for 18 h in a clinical study enrolling 10 healthy volunteers. A second clinical study examined the PK of delivering treprostinil at an average dose of 2.3 ng/kg/min to 5 healthy volunteers for 18 h. RESULTS: Relative to a design target of 0.042 mL/hr, the average flow rate of 23 PatchPumps operating for 48 continuous hours was 0.043 ± 0.007 mL/hr as tested in vitro. In vivo functionality was confirmed by complete infusion of saline for the entire duration with only mild and transient adverse effects. PK results with an infusion rate of 0.045 mL/hr of treprostinil resulted in mean Css of 297 pg/mL and T1/2 of 4.44 h, comparable to prior studies using conventional infusion pumps. CONCLUSIONS: The results of these studies demonstrate a successful proof-of-concept for the PatchPump technology.

Assessing the temperature of thermally generated inhalation aerosols.

BACKGROUND: Condensation aerosols are produced when a drug is vaporized and then cools in the inhalation air. Because energy is applied to vaporize the drug, there is a potential concern that the air temperature might not be well tolerated. A literature review indicates that the proper metric for this is the wet-bulb temperature (T(wb)) of the inhaled air. T(wb) measures the total energy of the air, including moisture content, and reflects the potential impact on safety and tolerability. METHODS: The Staccato® system (Alexza Pharmaceuticals, Mountain View, CA) uses thermal vaporization for aerosol generation and was used in a series of studies to characterize the peak transient value (peak T(wb)) of the air coming out of the device. These studies evaluated peak T(wb) over a range of air flow rates (15-45 L/min), ambient conditions [15-30°C and 15 to 90% relative humidity (RH)] and vaporization temperatures. RESULTS: Under nominal conditions (30 L/min air flow, 25°C and 50% RH), peak T(wb) was 28.8 ± 0.6°C (mean ± standard deviation). Over the range of operating conditions tested, mean values for peak T(wb) ranged from 26.2 to 33.3°C with similarly low variances. When operated under a combination of extreme conditions, peak T(wb) was measured to be 39.9 ± 0.1°C (mean ± standard deviation). CONCLUSIONS: Technical standards indicate that the upper limit on inhaled T(wb) for safety and tolerability is 50°C, and inhalation at that temperature can be sustained for 1 h. Peak values of T(wb) from the Staccato system are well below that threshold, approximately 30°C at nominal conditions and approximately 40°C at a combination of extreme conditions. Moreover, the peak lasts for only a few seconds, well under the time limit of 1 h. These results suggest that aerosols generated with the Staccato system will be safe and well tolerated.

In vitro aerosol characterization of Staccato(®) Loxapine.

Medicinal aerosol products (metered dose and dry powder inhalers) require characterization testing over a wide range of use and pre-operating stress scenarios in order to ensure robust product performance and support submissions for regulatory approval. Aerosol characterization experiments on Staccato(®) Loxapine for inhalation (Staccato Loxapine) product (emitted dose, particle size, and purity) were assessed at different operating settings (flow rates, ambient temperature and humidity, altitude, and orientation) and at nominal test conditions following exposure to various stresses on the device (mechanical shock, vibration, drop, thermal cycling, and light exposure). Emitted dose values were approximately 90% of the coated dose at every condition, meeting target specifications in each case. Aerosol purity was consistently >99.5% for every test setting, with no reportable impurities according to ICH standards (>0.1%). Particle size averaged 2µm (MMAD) and was independent of the different test conditions with the exception of different airflow rates. Particle size decreased slightly with airflow, which may assist in maintaining constant deep lung deposition. The combination of high emitted dose efficiency and a particle size range ideally suited for lung deposition, along with the consistency of these key aerosol attributes, suggests that the Staccato system has distinct advantages over more traditional aerosol systems.

Pulmonary delivery of therapeutic compounds for treating CNS disorders.

Delivering therapeutic compounds via the lungs presents potential advantages relative to other routes of administration. Depending on the compound and the disease state, these advantages may include: non-invasive medication delivery, ease of administration, higher bioavailability leading to dose sparing and lower systemic toxicity, potentially greater blood-brain barrier penetration and rapid pharmacodynamic effect. The practice of inhaling drugs has been around for centuries, including both medical and recreational usage. It is only more recently that formal clinical development programs have been undertaken specifically to use medication delivery via the lung to achieve systemic blood levels for the treatment of CNS disorders. At present, there are several CNS therapies being developed for pulmonary administration, with some of those programs at or near the marketing authorization stage. While there are still regulatory hurdles before these therapies can be put into practice, the success of these programs thus far demonstrates the scientific viability of inhalation therapies for treating CNS disorders.

In vitro aerosol deposition in the oropharyngeal region for Staccato loxapine.

BACKGROUND: The Staccato system employs a thermal vaporization technology to generate pure drug aerosols with a particle size optimized for alveolar deposition, leading to rapid absorption of the drug into the systemic circulation. Unlike most traditional aerosol-generation techniques, the particle size of the thermally generated aerosols is significantly affected by the airflow rate going through the device. The objective of this study was to determine the effects of flow rate and other operating conditions on predicted oropharyngeal and lung deposition when using the Staccato system. METHODS: In vitro oropharyngeal deposition was measured at airflow rates of 15-80 L/min through the device. Oropharyngeal deposition was also measured for different inhalation profiles, different ambient temperatures and humidities, and device orientations. Deposition was measured using the Alberta geometry model, which was derived based on information available in the literature, CT scans of patients, and observations of living subjects. RESULTS AND CONCLUSIONS: Deposition in the oropharyngeal geometry was consistently approximately 11% of the emitted dose throughout the entire range of flow rates. Such consistency in deposition was due to the fact that mass median aerodynamic diameter (MMAD) varied inversely as the square root of the flow rate, resulting in an approximately constant value for the inertial deposition parameter. Thus, an increase in flow rate, which would increase the momentum of a fixed particle size and generally lead to higher oropharyngeal deposition, was almost exactly counterbalanced by the accompanying decrease in MMAD. Results also showed that deposition in the oropharyngeal region was unaffected by other potentially relevant factors such as different airflow ramp rates, inhalation time, ambient temperature and relative humidity, and device orientations.

Effect of gender and device mouthpiece shape on bolus insulin aerosol delivery using the AERx pulmonary delivery system.

PURPOSE: A study was designed to compare differences in insulin aerosol deposition profiles in healthy male and female subjects, as well as examine the effect of mouthpiece cross-sectional shape, volume, and taper on deposition profiles using a developmental AERx pulmonary delivery system. METHODS: Six mouthpieces were screened in the laboratory, and three were selected for clinical investigation: a cylindrical mouthpiece with constant-cross-sectional area, an elliptical mouthpiece with constant-cross-sectional area, and a tapered elliptical mouthpiece with an exit cross-sectional area equal to one half the entrance cross-sectional area. RESULTS: There was no significant difference in the lung dose or in the deposition pattern between males and females (p > 0.05, by ANOVA). The cross-sectional shape of the mouthpiece had no significant effect on the clinical lung dose or the deposition pattern (p > 0.05, by ANOVA), although in vitro testing showed lower emitted dose values with the tapered elliptical mouthpiece (by ANOVA and Duncan's multiple range test, alpha = 0.05). Using the tapered mouthpiece in the clinic resulted in significantly more deposition on the mouthpiece itself when compared to the nontapered mouthpieces. CONCLUSION: Inhalation of insulin using the AERx system was insensitive to differences in male and female respiratory tract geometry across all mouthpiece designs examined.