WhichTrial Monthly Report · Issue 1
The US Clinical Trial Recruiting Pipeline
March 2026 → May 2026 — what gained ground, what slipped, what entered, and what left.
Published May 1, 2026 · Data through 2026-05 · By WhichTrial
The numbers at a glance
11,854
drugs in active recruiting trials (May 2026)
30,480
recruiting trials across 17 conditions
617
drugs exited recruiting since March
453
drugs entered recruiting since March
Two months of change. The recruiting pipeline shrank by 164 drugs on net. 254 drugs picked up additional recruiting trials, 368 lost ground but kept at least one open study, and 10,779 held flat.
Top gainers
Drugs that added the most recruiting trials between March and May. The list skews toward established cytotoxic and checkpoint-inhibitor backbones — but the most editorially interesting mover is much further down the table.
| Drug | Mar | May | Δ trials | Sponsors |
|---|---|---|---|---|
| Tirzepatide | 27 | 35 | +8 | 30 |
| Bevacizumab | 196 | 203 | +7 | 123 |
| Cyclophosphamide | 332 | 337 | +5 | 146 |
| Fludarabine | 190 | 194 | +4 | 90 |
| Temozolomide | 75 | 79 | +4 | 64 |
| Ivonescimab | 25 | 29 | +4 | 21 |
| Sacituzumab tirumotecan | 21 | 25 | +4 | 5 |
| Gemcitabine | 182 | 185 | +3 | 122 |
| Osimertinib | 41 | 44 | +3 | 36 |
| Orelabrutinib | 19 | 22 | +3 | 14 |
| Elacestrant | 15 | 18 | +3 | 15 |
| PF-08634404 | 6 | 9 | +3 | 1 |
| NNC0487-0111 | 1 | 4 | +3 | 1 |
| Capecitabine | 158 | 160 | +2 | 99 |
| Toripalimab | 79 | 81 | +2 | 46 |
Spotlight · Mover of the month
Tirzepatide accelerates: GLP-1 expansion isn't slowing
Tirzepatide is the only mover of its size in our May snapshot. Eli Lilly's GLP-1/GIP dual agonist — sold as Mounjaro for type 2 diabetes and Zepbound for obesity — went from 27 actively-recruiting US trials in March to 35 in May, a roughly 30 percent gain in eight weeks. The number of distinct sponsors running tirzepatide studies climbed from 23 to 30, and the number of indications attached to those trials rose from 57 to 66. Notably, the broader GLP-1 class is not moving in lockstep: semaglutide recruiting trials actually fell from 25 to 23 over the same window, and retatrutide slipped from 4 to 3. The acceleration is tirzepatide-specific.
What's striking is that Lilly itself sponsors only five of the 35 recruiting tirzepatide trials in our database. The other 30 are run by academic medical centers, NIH institutes, and a handful of other industry sponsors. That pattern — most of the recruiting footprint sitting outside the originator — has emerged in the wake of Lilly's recent regulatory wins. Zepbound's December 2024 FDA approval for moderate-to-severe obstructive sleep apnea, the SUMMIT Phase 3 readout in heart failure with preserved ejection fraction, and the SYNERGY-NASH Phase 2 hit (73 percent MASH resolution at the 15 mg dose vs. 13 percent on placebo)[1][2][3] have all widened the indication landscape. Recently-started tirzepatide trials (start dates Feb–Apr 2026) include the NIAAA studying metabolic alcohol-associated liver disease, MGH probing early-onset colorectal cancer prevention, UNC Lineberger looking at obesity-driven endometrial cancer, St. Jude testing it in childhood-cancer survivors, and a Phase 3 placebo-controlled study from a sponsor called Hudson Biotech (NCT07481747). Lilly's own Phase 3 MASH master protocol (NCT07165028) anchors the liver-disease push.
For the broader pipeline, what we observe is that tirzepatide is being used as a comparator and adjunct, not just as a study drug in its own right. Recruiting trials in oncology supportive care, transplant medicine, opioid use disorder, knee osteoarthritis, and HIV-associated inflammation all include it as a metabolic lever rather than the primary agent under investigation. Whether that translates into meaningful trial-site capacity pressure on adjacent metabolic programs is something we'll be watching across the next several monthly snapshots. Lilly's next-generation triple agonist retatrutide also remains in active Phase 3 development, though its current recruiting footprint in our dataset is small (3 trials in May, down from 4 in March).
Top losers
Drugs that lost the most recruiting trials but still have at least one study open. A drop here means trials have moved out of the recruiting phase — either they completed enrollment, were terminated, or moved to active-not-recruiting status.
| Drug | Mar | May | Δ trials | Sponsors |
|---|---|---|---|---|
| Pembrolizumab | 447 | 431 | -16 | 239 |
| carboplatin | 320 | 307 | -13 | 169 |
| Sacituzumab govitecan | 44 | 34 | -10 | 27 |
| Tazemetostat | 12 | 4 | -8 | 4 |
| Dexamethasone | 163 | 156 | -7 | 100 |
| Pemetrexed | 117 | 110 | -7 | 73 |
| Cisplatin | 261 | 255 | -6 | 151 |
| Lenalidomide | 88 | 82 | -6 | 59 |
| Metformin | 59 | 53 | -6 | 47 |
| Venetoclax | 192 | 187 | -5 | 99 |
| Doxorubicin | 101 | 96 | -5 | 64 |
| Obinutuzumab: | 62 | 57 | -5 | 34 |
| Nivolumab | 176 | 172 | -4 | 105 |
| Nab paclitaxel | 126 | 122 | -4 | 80 |
| Etoposide | 99 | 95 | -4 | 70 |
Spotlight · Plateau watch
Keytruda decelerates: a maturing IV franchise rotates into ADCs and Qlex
Pembrolizumab's recruiting footprint dropped from 447 to 431 trials between March and May 2026, the largest absolute decline on the board. The footprint we track is dominated by Phase 1 and Phase 2 investigator-led combinations — only 77 of the 431 active trials are Phase 3, and Merck itself sponsors just 32 of them; the rest sit at academic medical centers, the NCI, and other co-sponsors. Among the trials that fell out of recruiting status in the period, the visible pattern is mostly late-stage academic combination studies (Dana-Farber, MSKCC, NCI, Northwestern) reaching their enrollment caps with completion dates in 2026, alongside an Amgen biosimilar PK study (NCT06430866). What we can't tell from the snapshot alone is whether the −16 reflects normal trial-program lifecycle or something more structural — Merck doesn't publicly distinguish between the two.
What is publicly documented is the broader Merck pipeline activity surrounding pembrolizumab. The September 2025 FDA approval of Keytruda Qlex (pembrolizumab co-formulated with berahyaluronidase alfa-pmph) generated $128M in its first full quarter, and CEO Rob Davis has guided to 30–40% US patient conversion by 2027, which Merck has framed as a key lever ahead of the 2028 US composition-of-matter patent cliff [2][3]. The KEYNOTE-A86 NSCLC non-inferiority trial backing the SC switch is still recruiting and reads out in October 2026 [5]. Separately, on the April 30 Q1 earnings call, management framed sacituzumab tirumotecan (sac-TMT, the Kelun-partnered TROP2 ADC) as a “cornerstone and workhorse” with 17 Phase 3 studies underway, 13 of them first-mover, and the first sac-TMT/Keytruda combo readout in 1L NSCLC just printed [1] — sac-TMT also grew +4 trials in our March-to-May window. The 2023 Merck/Daiichi Sankyo deal ($4B upfront, up to $22B) covering three DXd-ADCs is also still active [6]. We're flagging these as context, not as a verified causal explanation for the −16.
Across the rest of the PD-1/PD-L1 class, the picture is mixed rather than category-wide saturation. Nivolumab is also off (−4) but the rest is flat-to-positive in our snapshot: Atezolizumab unchanged, Durvalumab −2, Tislelizumab +1, Cemiplimab +2, Toripalimab +2. Regeneron's October 2025 adjuvant CSCC approval and its Libtayo-as-backbone strategy across 30+ tumor types — including combinations with fianlimab (LAG-3) — suggest cemiplimab has continued runway[7]. Coherus/Junshi's Loqtorzi grew Q2 2025 net revenue 36% year-over-year off the late-2023 NPC approval, with Phase 1b/2 expansion data in HCC, HNSCC, gastric, and esophageal expected through 2026 [8]. Whether the pembro decline persists into the next snapshot, and whether competitor gains continue, is what we'll be tracking.
- [1]Merck Q1 2026 earnings call (Apr 30, 2026) — sac-TMT framing
- [2]Merck press release — Keytruda Qlex FDA approval (Sept 19, 2025)
- [3]BioSpace — Davis 30–40% conversion target
- [5]AJMC — KEYNOTE-A86 (NCT04956692), Phase 3 SC vs IV NSCLC
- [6]STAT News — Merck/Daiichi Sankyo $22B ADC deal (Oct 2023)
- [7]Regeneron IR — Libtayo adjuvant CSCC approval (Oct 2025)
- [8]Coherus Oncology Q2 2025 results — Loqtorzi growth
Drugs that left recruiting
617 drugs that had at least one recruiting trial in March no longer do in May. Most are long-tail compounds with one or two trials that completed enrollment; a handful are clinically meaningful.
New entrants
453 drugs began recruiting between March and May that hadn't previously appeared in our snapshot. Most are early-phase, single-sponsor studies — first signals of new programs.
About this report
Data source. All figures are derived from the public ClinicalTrials.gov registry, queried monthly. We track US-based recruiting trials across 17 condition categories and ~50 metro areas.
What “recruiting” means. A trial is recruiting when ClinicalTrials.gov flags its overall status as RECRUITING. When a trial no longer appears in our monthly fetch, we mark it as “not recruiting” — it may have completed enrollment, been suspended, terminated, or moved to active-not-recruiting status. We don't distinguish between those states in the aggregates above.
What “exited” means. A drug exited recruiting if it had at least one trial flagged RECRUITING in March 2026 and has zero such trials in May 2026. The drug itself isn't gone — its open trial pipeline is.
Limitations. Our extraction filters out generic terms (placebo, chemotherapy, radiation, saline) and intervention names longer than 60 characters, so very long trial-arm descriptions aren't counted as drugs. Some drugs appear under multiple aliases; we deduplicate where we can.