PSG: Specialty drug spending predicted to increase 32% by 2028

Specialty drug spending increased 12.5% after rebates in 2025, according to new research by Pharmaceutical Strategies Group (PSG). Gross specialty drug costs increased to $1,548 per member per year, while net costs reached $1,251 per member per year. Looking ahead, PSG projects that gross PMPY specialty costs will jump by another 32% by 2028.

“Specialty is being driven by utilization,” Morgan Lee, PSG's VP of research and marketing, said in an interview. “We are seeing more members taking specialty drugs. We’re seeing the percentage of members on specialty drugs continues to rise. It is going up every single year.”

The share of members using at least one specialty drug also rose from 4.4% in 2023 to 5.5% in 2025. These findings suggest the increased spend is now being driven by more patients using specialty therapies.

Biosimilar adoption has likely played a role in reducing the role of cost per claim in specialty drug trends, while new drug approvals and expanded indications for existing drugs have fueled increased specialty drug utilization.

Overall biosimilar market share increased from 22.6% in 2023 to 56.3% in 2025, with Humira (adalimumab) biosimilars playing a major role, according to PSG. Humira biosimilars climbed from 0.3% market share in 2023 to 82.4% market share in 2025, while Stelara (ustekinumab) biosimilars reached 18% market share in their first year on the market.

“Humira went from being the number one drug by spend in our 2024 report, and by 2025, it had dropped out of the top 10,” Lee said. “This was because PBMs had implemented their Humira biosimilar strategies. Now we're seeing an entirely different set of top drugs.”

But inflammatory medications are still the top category in specialty drug spending. “Eight of the top 10 drugs are inflammatory. If you're a payer looking at your strategies in terms of utilization management and coverage decisions, it's a big one.”

The two drugs at the top of PSG’s specialty spend in 2025 are the anti-inflammatory drugs Skyrizi (risankizumab-rzaa) from AbbVie and Sanofi/Regeneron’s Dupixent (dupilumab). Skyrizi is used to treat psoriasis, Crohn’s disease and ulcerative colitis. Dupixent is approved to treat atopic dermatitis, asthma, COPD and other inflammatory conditions. Expanded indications, direct-to-consumer advertising, and shifting utilization following the introduction of Humira and Stelara biosimilars likely contributed to the increase in spend for these drugs, PSG said in the report.

Stelara, which is approved to treat psoriasis, Crohn’s and ulcerative colitis, was still among the highest in terms of spend in the PSG report. The biosimilars that reference Stelara began launching last year, and Lee said the biosimilars will likely have a bigger impact this year as PBMs and plans continue to work through their strategies.

Rebates are still part of the equation for both branded products and biosimilars, and this could be true for Stelara, Josh Van Ginkel, VP of plan sponsor consulting at PSG, said in an interview. “We saw this with Humira as the biosimilars started taking off. The manufacturers started offering deeper discounts on the back end. PBMs have different strategies that drive what’s on the formulary and what’s preferred. Some of the benefit that we had anticipated seeing from biosimilars was eaten up by patients moving to other more expensive brand drugs,” he said.

PSG expects specialty drug spend to keep rising, driven by new, typically higher-priced drugs entering the pipeline and by expanding indications that bring more patients into treatment, Lee said.

Van Ginkel said regulatory pressure from the White House, Congress and state insurance departments could eventually push specialty prices down, and some employers are already removing high-cost specialty drugs from coverage, pushing patients to choose between paying out of pocket or switching to a covered alternative.

Non-specialty trends

For the 2025 report, PSG added a new section on non-specialty drugs, a change prompted by the growing use of GLP-1s for diabetes and obesity. Historically, non-specialty spend grew slowly and drew little payer attention; that is no longer the case. “In non-specialty, there’s this combination of expensive drugs, as well as more people taking those drugs,” Lee said.

She said diabetes alone accounts for about a third of spend in non-specialty spend, but overall spend is being pushed up largely as a result of the use of GLP-1s for weight loss. Obesity drugs account for only about 4% of non-specialty pharmacy spend on average, Lee said, but that figure can climb past 20% for employers with broad GLP-1 coverage for weight loss.

Van Ginkel said roughly a third of large employers his practice works with, generally those with more than 10,000 covered lives, now cover GLP-1s for weight loss, a figure he said aligns closely with PSG's survey data.

Employers are pursuing two distinct strategies, Van Ginkel said: some pay for counseling and lifestyle programs to extend and sustain weight-loss results, while others focus on controlling spending directly through prior authorization, body mass index requirements, and, less commonly, prescribing networks limited to weight-management specialists. PSG’s data shows heavy use of BMI and prior-authorization requirements but low uptake of prescriber-network restrictions.

Both Lee and Van Ginkel predict that prices for GLP-1 drugs will decrease as more products become available, and it’s likely plans and employers will increase their coverage. “I tend to see more coverage of GLP-1s for weight loss in highly competitive hiring markets,” Van Ginkel said. “In those competing for software programmers or nurses or other areas that are very difficult to hire and retain employees with high skill levels, we tend to see more coverage of GLP-1s because they need to offer a competitive benefit.”