An example of RWD analysis of the IgA Nephropathology field
Thinking of endemic versus rare disease promotion, I'm reminded of Tolstoy's line "All happy families are alike; each unhappy family is unhappy in its own way," there are commonalities in the playbook for a disease 1 in 5 Americans have, or at least there was. It's TV – at launch, your target market is a huge swath of the population, so the only thing that matters is maintaining discipline in price efficiency of media buying against the largest population possible.
For those conditions, the patient is already aware of the condition: for instance I know I am clinically obese, and the competition is whether I become more aware of the efficacy or other value proposition of a drug. We see this with the GLP-1 fight of course, with battles over which causes the most weight loss leading to lawsuits, and now with the launch of oral wegovy and foundayo leading to messaging wars over convenience. Often a new brand coming to market might suggest another benefit, such as a time-release dimension, lower reported side effects, or other capability which makes use of the drug less burdensome, boosting adherence and improving patient experience.
In rare disease the same assumptions don't hold, one often starts from a position of people not even knowing what the condition means, depending on rarity even at the provider level. We define "rare" in line with the Orphan Drug Act's line of less than 200,000 patients, though a rare disease of 10,000 faces far different challenges than one with 100,000. The efficiencies of scale simply do not play- you're just going to expend a massive amount more to diminishing returns. It's something we often consider when evaluating different approaches to consumer engagement, if the true population is small enough you can't buy your way to an efficient engagement rate, you have to think differently.
The IgA nephropathy (IgAN) market is just such a case. IgAN is part of the broad category of autoimmune conditions the current wave of precision medicine techniques is solving for, and doing so in spades. There are now six distinct mechanisms of action for treating it either fully FDA approved or under accelerated approval, all since just 2023. For a relatively small market, this is a tremendous amount of attention.
Alongside finally having treatments, diagnostic guidance has been updated to look for the disease sooner, and this is perhaps the most interesting thing to me about the market: how we can see the diagnostic journey accelerating in real time.
Across PurpleLab's own data, the average time from biopsy-confirmed diagnosis to disease-modifying therapy (DMT) initiation fell from 1,447 days before 2024 to 192 days in the 2024–2026 era — an 87% reduction, driven directly by new-therapy availability. This radically transforms how we need to think about the patient pools along the care journey and revise the time-bounding of how long patients sit at different levels of the funnel.
In 2025 it was 122 days, in 2024 it was 198, the year before 362. This time to treatment is a huge shift, and makes IgAN diagnosis pipelines far faster than other rare diseases, which can take years to properly identify.
53 days is the good scenario though, all to often in rare, what you're really trying to trap for is the missed, the undiagnosed, the dogs that don't bark. We don't just need to make sure the specialist is ordering the biopsy, we need to make sure the primary is referring to the specialist (nephrologist, in this case) in a timely manner. Looking at the disease presentation, the majority of IgAN patients come from PCPs, with a quarter coming through ERs and community care settings. In both cases, a large proportion fall into a long cycle of watchful waiting from the PCP's, only 35% get the test that would indicate potential IgAN diagnosis. The -patients who do receive UPCR testing get up to 12.8 repeat orders on average during non-specialty monitoring, suggesting the signal is often present well before referral. Halving that can meaningfully pull forward time to diagnosis for an enormous segment of the patient population, so effective non personal promotion should include making sure PCPs are aware of the revised testing guidelines.
So, your mean patient has never heard of the disease, your median PCP doesn't know they should be moving the patient to a specialist sooner, what about our modal nephrologists? Well, they're now looking at six different tools to solve the problem, and the brand's job is to make sure they know the utility of their particular medication. IgAN is an in-between sort of rare disease- big enough to be at the top end of rare, small enough that the field force the brand employs may still be quite small. There's over 10,000 practicing nephrologists in the country, so effective engagement of that set of treaters has to be extremely tactically sound.
For the full 18 page TA analysis including prospective recommended tactics, segmentation, and approaches, send me a linkedin dm or email me at tsweetser@purplelab.com
Originally published on LinkedIn.