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For a long time, about 2 mL marked the edge of what a handheld injector could deliver. Past that point, a dose no longer fit standard prefilled syringe or cartridge systems, and companies looked elsewhere, often to on-body wearable injectors.
We recently sat down with Windgap Medical’s Aaron Mann to see whether wearables are truly the future of high-volume delivery, or whether advances in formulation and device technology continue to open up other options.
Aaron’s perspective is that it depends on the molecule, and that the line between handheld and wearable may end up being drawn by injection time as much as by injection volume.
He brings a rich and uncommon mix of vantage points. Windgap Medical develops handheld autoinjectors for drugs that don’t fit into conventional autoinjectors due to viscosity, stability complexity, or volume.
Before that, Aaron ran 3M’s drug delivery systems business and led its carve-out with investors to form Kindeva Drug Delivery, where he was CEO. Earlier, he ran corporate development at Phillips-Medisize. In all, he’s spent about 12 years in drug delivery across devices, formulation, and CDMO services, and has seen the volume problem from the manufacturing floor, the pharma partner side, and the inventor’s bench.
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Aaron’s key insights and practical takeaways
If you’re short on time, here are the most important lessons from the discussion.
Wearable decisions are usually driven by volume. Once a handheld dose reaches about 2 mL, you move beyond standard prefilled syringe and cartridge-based systems. That threshold has historically pushed companies toward other solutions.
There are three main routes past the ceiling, and pharma usually tries formulation first. Most pharma are chemistry or biology companies at heart, so engineering a better formulation tends to be the first stop. Enzyme-assisted approaches and permeation enhancers are a close cousin. Device solutions are getting more attention as the industry learns how successfully patients can self-administer outside a healthcare setting, which can benefit patient experience and potentially total cost. In the end, it really comes down to the molecule.
Enzyme-assisted delivery works by temporarily making room. Aaron described these as additives that temporarily create space in the subcutaneous tissue so a larger volume of fluid can be placed there and then absorbed naturally. He cited Halozyme as a company that has built a business in this space and described the effect as clearing space that the body naturally refreshes over about 24 hours.
Its biggest advantage is that it’s proven. Products using this approach are on the market and accepted by regulators and patients, which appeals to companies with a degree of risk aversion. It has helped move IV products to subcutaneous delivery, with a number of examples in oncology.
Its trade-offs are usually time, cost, and licensing. Adding a component means reformulation and compatibility studies, and often effectively creating a new product. There’s usually a licensing relationship with the enzyme provider, with economic implications. And it doesn’t solve reconstitution, mixing, or two-drug delivery challenges.
The 3 to 10 mL range matters because of biologics and the shift from IV. Biologics and biosimilars are physically larger molecules. Large-volume doses have historically lived in IV delivery, which generally calls for a healthcare professional overseeing line insertion. Moving those doses into the subcutaneous space makes self-administration easier and safer for patients, and that’s where devices that support larger self-injected volumes come in.
A recent approval shows the demand and the limits of the blueprint. Nick asked about the FDA’s approval of an autoinjector version of a therapy that previously required a multi-hour wearable infusion. Aaron called it an impressive reformulation of a small molecule, concentrated to roughly 10 times what the original wearable required. Small molecules don’t face the viscosity problems biologics do, so it’s a somewhat limited blueprint. But it shows that even when a drug is already working in an on-body injector, there’s market demand for a handheld option that’s easier or faster to use.
Concentrating biologics runs into viscosity, stability, and aggregation. Aaron prefaced this by saying he isn’t a chemist or biologist. As monoclonal antibodies are concentrated, viscosity rises, and pushing a thicker liquid through a thinner needle creates problems for the system, including patient pain and discomfort. Stability and aggregation become concerns too. He thinks the industry is starting to push against those limits, though he said he certainly wouldn’t bet against the world’s best formulators.
Combination therapies add another layer. As two-drug treatments become more common, companies have to ask whether the products play nicely together over the intended shelf life, and what co-formulation means for manufacturing.
A device solves the problem differently. Formulation changes the drug product. A device changes how you deliver the molecule you already have. Windgap’s approach is to innovate around standard primary packaging: cartridges, stoppers, and other components pharma already knows, trusts, and has supply chains for, so partners aren’t asked to revalidate the primary container. Its system uses two cartridges, gas power, and standard needles.
Want to go deeper? Aaron and his Windgap colleagues Dr. Brent Buchine and Mike Ratigan wrote about this in ONdrugDelivery’s September/October 2026 issue. Their article, The Missing Middle of SC Drug Delivery: How a Dual-Cartridge Architecture Could Unlock the 3–10 mL Opportunity, argues that the traditional 2 to 3 mL limit for subcutaneous injection says more about conventional device and container design than about what patients or products need.
Patient expectations keep rising, and history shows why. Aaron told the story of a young girl with asthma in the mid-1950s who asked her father why her medicine couldn’t be as easy to use as a can of hairspray. Her father ran the company that later became 3M’s drug delivery business, and her question led to the metered-dose inhaler. Insulin followed a similar arc, from vials and syringes to pens, and taught the industry how well people without medical training can manage chronic conditions. Epinephrine autoinjectors extended that to acute situations. Each step raised the bar for what patients expect.
Patients may tolerate up to 10 mL. Holding the device steady is the harder part! Aaron said the industry largely knows that patients can tolerate up to 10 mL in a subcutaneous injection, with some studies challenging the conventional wisdom. The bigger challenge may be holding an autoinjector steady: keeping a fine-gauge needle in place, possibly pressing a plunger, avoiding movement that could let medication escape, and watching the device. He sees delivering 10 mL in 30 seconds or less as the goal, and achievable, with work still to do.
Wearables are genuinely the better choice in some cases. Above 10 mL, wearables make sense, and at those volumes it may be therapeutically preferable to deliver over 30 minutes or a couple of hours. Infrequent dosing is another case. Weekly injections, like many GLP-1 regimens, become routine. Monthly, every-six-weeks, or quarterly dosing makes it harder to remember every step in the right order.
Two injections instead of one raises its own questions. Asked whether a 20 mL dose could simply be split into two injections, Aaron deferred first to the underlying science on whether that’s equally effective. Assuming it is, sites need to be separated, and you have to be confident a patient will complete not one but two injections back to back with equal success.
Wearables have their own human factors questions. How does the adhesive interact with skin? What’s it like to put on, wear for an extended period, and take off? Where is it placed, will people bump it or worry about bumping it, and will they fidget with it? How does the device signal that dosing is complete, and if that involves connectivity, what does that add? In his words, it’s all about getting to the right questions and asking them really thoughtfully to help patients succeed.
Committing early to the wrong format is expensive to undo. Switching delivery devices later means repeating usability and human factors work, bridging to the new presentation post-approval across every regulatory regime you’re in, and managing a lifecycle switch through the entire supply chain, from device and primary container manufacturing to channel inventory and customer contracts.
Five questions to answer before choosing a wearable. Aaron’s list:
What’s the real volume and viscosity at the concentration you can actually make at scale, given your commercial plans, and what does that mean for supply chain and cost of goods?
How frequently is it dosed?
How successful is this patient population with devices? Consider pediatric patients, people over 65, and those with musculoskeletal or dexterity issues.
Does the drug need reconstitution or mixing, or is it a combination therapy that requires simultaneous delivery?
Run all of that back through your supply chain. Can you deliver the volumes, on the timeline, with the shelf life and cost of goods you need?
Where the line may settle. Looking five to 10 years out, Aaron expects handhelds to settle at up to 10 mL, with most chronic self-injected biologics ending up in a handheld autoinjector form factor. He sees wearables remaining very effective for larger doses, longer durations, and very infrequent dosing. Ultimately, he thinks the industry is dividing these categories as much by injection time as by injection volume.
He closed by noting what an exciting time it is to work in self-administered drug delivery, and thanked the customers, collaborators, and competitors he works alongside in service of patients.
One thing to bring back to your team
Aaron’s first question is the one most likely to be answered a little too optimistically: what is the real volume and viscosity at the concentration you can make at scale?
A development concentration that works at the bench may not be the concentration you can manufacture commercially. If your device decision rests on the bench number, and the commercial number turns out to be higher, you may be looking at the expensive mid-lifecycle switch he described.
It’s worth confirming which number your device strategy is actually built on.
Aaron Mann is CEO of Windgap Medical, a drug-device combination product company developing handheld autoinjector platforms for complex injectables, a role he has held since 2023. Aaron has over 20 years of experience in the medical device and pharmaceutical services industries across a variety of leadership roles. Before joining Windgap as the CEO in 2023, Aaron served as the founding CEO of Kindeva Drug Delivery, a complex drug CDMO focused on respiratory and transdermal combination products. He built Kindeva in partnership with 3M and Altaris Capital Partners following 3M’s divestiture in 2019. He has prior executive leadership roles at Phillips-Medisize, 3M, and Remedi SeniorCare. He holds an MBA from Harvard Business School and a BA from Carleton College.
Connect with Aaron on LinkedIn here.
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