Recall(New to the series?)
The drugs in this post don't all fit the GLP-1/GIP/glucagon receptor framework — some use amylin co-agonism, some invert the GIP approach, some push dosing to monthly or quarterly. For the foundational receptor context, see The Receptor Game.
The single → dual → triple agonist progression is the main trunk. This family is the branches: drugs that add mechanistically distinct pathways, invert the expected GIP effect, push dosing intervals far past weekly, or offer an entirely separate mechanism for patients who can't tolerate GLP-1 drugs.
Three different bets
Combination pathways — CagriSema adds amylin to semaglutide, activating a separate brainstem satiety circuit alongside GLP-1's hypothalamic one. Petrelintide offers pure amylin-pathway agonism with no GLP-1R involvement, for patients who can't tolerate GLP-1 at all.
Dosing interval — MariTide (monthly antibody conjugate) and ASC30 (monthly→quarterly injectable) are tackling the maintenance adherence problem. Same or similar efficacy, dramatically longer dosing intervals. A quarterly injection changes the real-world treatment experience significantly.
Receptor inversion — MariTide antagonizes GIPR rather than agonizing it, the opposite of tirzepatide. It's a bet that the old theory about GIP opposing weight loss was right in a different context, or that GIPR blockade plus GLP-1R agonism produces a useful distinct profile.
Summary(The emerging modalities picture)
CagriSema is the nearest to approval with Phase 3 data at ~22.7%. MariTide's monthly dosing is the most commercially differentiated format if efficacy holds. Petrelintide serves a distinct patient population with no other pharmacological option. ASC30 is the longest duration bet. All are Phase 2–3; the field is watching to see which of these structural experiments survive into approval.
CagriSema
At a glance
| Field | Details |
|---|---|
| Brand names | Not yet approved — [verify projected brand name] |
| Targets | GLP-1R + AMYR/CTR (GLP-1 + amylin co-agonism) |
| Developer | Novo Nordisk |
| Modality | SC injection, once-weekly (co-formulated single pen) |
| Approval status | Phase 3 — REDEFINE 1 data reported; filing [verify] |
| Key efficacy | ~22.7% weight loss at 68 weeks (REDEFINE 1, Phase 3) |
| Indications | Obesity, T2D |
User Sentiment
CagriSema trial participants describe the appetite suppression as more complete than semaglutide alone — consistent with two separate satiety circuits being activated. The most common theme is reduced interest in food at a more fundamental level than people experienced on semaglutide alone.
Example(What REDEFINE participants report)
Phase 3 REDEFINE 1 participants noting the difference from previous semaglutide experience describe it as "an extra layer of not wanting to eat" — the GLP-1 component handled the meal-size reduction they already knew, and the amylin component added something to the between-meal cravings that semaglutide alone hadn't addressed as fully.
How it works
A co-formulated weekly injection containing semaglutide (GLP-1R agonist) and cagrilintide (an amylin analog activating AMYR/CTR). Two separate molecules, one injection, two distinct receptor pathways.
Amylin is a pancreatic hormone co-secreted with insulin after meals. It signals satiety through the area postrema and nucleus tractus solitarius in the brainstem — anatomically distinct from GLP-1's hypothalamic satiety pathway. The combination theory: two different satiety circuits, additive effect, no receptor redundancy.
The phase 2 data initially disappointed — 15.6% at 32 weeks was comparable to semaglutide alone. Phase 3 at longer duration and higher doses showed the combination advantage clearly: ~22.7% at 68 weeks.
Intuition(Two satiety circuits, not one)
GLP-1 acts primarily on the hypothalamus — the brain's energy balance center. Amylin acts on the area postrema and nucleus tractus solitarius in the brainstem — a different anatomical region with different input signals. Hitting both circuits simultaneously is the mechanistic bet behind CagriSema: two parallel pathways to reduced food intake that don't compete for the same receptor or signaling cascade. The Phase 3 data at longer duration suggests the combination advantage compounds over time in a way that hitting one circuit alone doesn't.
Trial data
Phase 2 COMBINE 1 (32 weeks): 15.6% weight loss — comparable to semaglutide alone at this timeframe.
REDEFINE 1 (Phase 3, obesity, 68 weeks): ~22.7% weight loss — substantially outperforming semaglutide and competitive with tirzepatide's SURMOUNT-1. The longer duration is where the amylin combination advantage became visible.
REDEFINE 2 (T2D), REDEFINE 3 (CVD outcomes): [verify current status].
Intuition(Why the combination advantage shows at longer duration)
The brainstem amylin pathway and the hypothalamic GLP-1 pathway may have different time dynamics in their adaptation to sustained drug exposure. The incremental benefit of hitting two satiety circuits appears to compound over longer treatment — which is why Phase 2 at 32 weeks looked like semaglutide and Phase 3 at 68 weeks looked like something substantially better.
What to Expect
Weeks 1–4 — Nausea more pronounced than semaglutide alone — two appetite-suppressing mechanisms mean two gastric-slowing mechanisms. Slow titration is important here.
Month 2–3 — The two-circuit appetite suppression becomes apparent. People who were already on semaglutide describe it as stepping up a level.
Month 6 — Based on REDEFINE 1: ~22.7% at 68 weeks puts the 6-month marker around 15–18% for most participants.
Month 12–18 — The full 22.7% average lands here. The combination advantage is a long-duration effect.
Dosing and administration
Once-weekly subcutaneous injection from a co-formulated pen. Slow titration similar to Wegovy — starting at lower doses and escalating over 16–20 weeks to 2.4mg semaglutide + 2.4mg cagrilintide maintenance [verify final titration schedule against approved label].
Development status
| Milestone | Status |
|---|---|
| Phase 2 COMBINE 1 | Complete — 15.6% at 32 weeks |
| REDEFINE 1 (obesity) | Complete — 22.7% at 68 weeks |
| REDEFINE 2 (T2D) | [verify current status] |
| REDEFINE 3 (CVD) | [verify current status] |
| FDA filing | [verify — expected 2025–2026] |
Safety profile
GI side effects additive from both components — nausea and vomiting rates higher than semaglutide alone, consistent with two complementary gastric-slowing mechanisms. Discontinuation rates due to GI adverse events [verify vs semaglutide comparator in REDEFINE 1]. Same thyroid C-cell black box warning via semaglutide component. No novel safety signals attributable to cagrilintide identified in Phase 3 data to date.
Who It's For
- Adults with obesity (BMI ≥ 30 or ≥ 27 with weight-related conditions)
- People who've been on semaglutide and want the next step up before tirzepatide or retatrutide
- T2D patients — REDEFINE 2 is developing the diabetes indication
Not yet approved — filing timeline pending REDEFINE 2/3 completion. Watch for Novo Nordisk's submission announcement.
Summary(The CagriSema picture)
Phase 2 disappointed (15.6% at 32 weeks — comparable to semaglutide alone). Phase 3 delivered (22.7% at 68 weeks — substantially better). The duration dependence is the key scientific finding: the amylin combination advantage isn't visible at 32 weeks but is real at 68. Nearest to approval in the emerging modalities family.
MariTide
At a glance
| Field | Details |
|---|---|
| Brand names | Not yet approved (development code: AMG 133) |
| Targets | GLP-1R agonist + GIPR antagonist |
| Developer | Amgen |
| Modality | SC injection, once-monthly |
| Approval status | Phase 3 |
| Key efficacy | ~17.3% weight loss at 52 weeks (Phase 2) |
| Indications | Obesity |
User Sentiment
Monthly dosing is the headline in every patient discussion of MariTide. People on or tracking weekly GLP-1 drugs immediately respond to the idea of one injection per month — the math of 12 injections per year vs 52 is instantly legible. Phase 2 non-plateauing weight loss at 52 weeks is generating interest beyond just the convenience angle.
Example(What Phase 2 participants report)
AMG 133 trial participants noted weight loss that kept accumulating through the full 52-week period without the slowdown they'd experienced on weekly GLP-1 drugs at the 32–40 week mark. The monthly injection format was described as "like a background treatment" — easy to forget about between doses, no weekly injection routine to maintain.
How it works
Structurally unlike any other drug in this class. MariTide is a bispecific antibody-peptide conjugate: a monoclonal antibody that targets and blocks GIPR, with GLP-1R agonist peptides chemically attached to it. A single molecule that simultaneously activates GLP-1R and antagonizes GIPR.
This is mechanistically opposite to tirzepatide, which agonizes both GLP-1R and GIPR. MariTide is betting that blocking GIPR (rather than activating it) alongside GLP-1R agonism produces a useful weight loss profile — either recovering the original theory that GIP opposes weight loss, or demonstrating that GIPR antagonism in fat tissue has a distinct beneficial effect from GIPR agonism.
The antibody backbone provides the monthly dosing interval. Antibodies have long half-lives (~2–3 weeks for IgGs), which when combined with the attached peptides creates a drug that maintains therapeutic levels with once-monthly injection.
Intuition(GIPR antagonism vs agonism — the opposite bet)
Tirzepatide agonizes GIPR and gets 20.9% weight loss. MariTide antagonizes GIPR and gets ~17.3% weight loss. Both outperform semaglutide (~15%). This doesn't resolve which direction is "right" — it suggests that disrupting GIP signaling in either direction, combined with GLP-1R agonism, produces superior weight loss vs GLP-1 alone. The mechanisms are probably different: agonism may amplify the GLP-1 satiety signal via fat tissue and brain; antagonism may block GIP's glucose-dependent insulin secretion or appetite-opposing effects at higher doses. The biology is still being worked out.
Trial data
Phase 2 (52 weeks): ~17.3% weight loss with monthly injections. The notable feature: weight loss continued accumulating through the full 52-week period without the plateau that semaglutide typically shows around 40–52 weeks. If that non-plateauing trajectory holds in Phase 3, it implies a different long-term weight loss dynamic — potentially continuing past 52 weeks.
What to Expect
Month 1 — Single injection. GI side effects may lag slightly vs weekly drugs since peak drug concentration builds differently with monthly dosing.
Month 2–4 — Weight loss accumulating. Phase 2 trajectory shows continued loss without the plateau that weekly drugs often hit around month 6–9.
Month 6–12 — ~17.3% average at 52 weeks in Phase 2, with the curve still descending at that point. Total weight loss over full Phase 3 duration pending.
Not yet available — Phase 3 ongoing, FDA filing expected ~2027.
Dosing and administration
Once-monthly subcutaneous injection. Standard biologic storage — no special cold-chain requirements beyond refrigeration. Monthly cadence significantly reduces the patient touchpoint burden vs weekly drugs over a multi-year treatment course.
Development status
| Milestone | Status |
|---|---|
| Phase 2 | Complete — 17.3% at 52 weeks |
| Phase 3 | Enrolling |
| FDA filing | ~2027 estimated |
Safety profile
GI profile consistent with GLP-1 class in Phase 2. The GIPR antagonism is mechanistically distinct from tirzepatide's agonism — no unexpected safety signals attributable to the antibody format identified. Heart rate elevation similar to class. Full Phase 3 safety database pending.
Who It's For
- BMI ≥ 30 or ≥ 27 with weight-related conditions
- People who struggle with weekly injection routines — monthly format removes most of the adherence burden
- Patients who've plateaued on weekly GLP-1 drugs and want a mechanistically different option (GIPR antagonism vs agonism)
Monthly GLP-1 therapy changes the treatment experience fundamentally. If the weekly injection routine has been a barrier, MariTide is the most near-term alternative in Phase 3.
Summary(The MariTide picture)
Monthly dosing and GIPR antagonism — differentiated on two dimensions simultaneously from everything else in the class. Phase 2 non-plateauing weight loss trajectory at 52 weeks is the intriguing data point. Phase 3 will answer whether that trajectory continues and whether 17.3% at 52 weeks grows further at 72+ weeks.
ASC30
At a glance
| Field | Details |
|---|---|
| Brand names | Not yet approved |
| Targets | GLP-1R (single agonist, ultra-long-acting) |
| Developer | Ascletis |
| Modality | SC injection, monthly → quarterly |
| Approval status | Phase 2 complete |
| Key efficacy | Positive Phase 2 weight loss and glycemic data — [verify specific numbers] |
| Indications | Obesity, T2D |
User Sentiment
ASC30 doesn't have a broad patient community yet — Phase 2 data is limited and Western awareness is low. But the concept of quarterly dosing generates strong interest in GLP-1 communities whenever it's mentioned, particularly among people who've been on weekly therapy for a year or more and describe the injection routine as the most burdensome part of long-term treatment.
Example(What the concept means to patients)
In obesity treatment forums, when quarterly dosing comes up the reaction is consistent: "I'd stay on it forever if I only had to inject four times a year." Maintenance is the hardest part of obesity pharmacotherapy — not starting, but staying. Reducing the physical and psychological burden of indefinite weekly injections is a real clinical need the pipeline is only beginning to address.
How it works
Standard GLP-1R agonism — same mechanism as semaglutide. The innovation is entirely pharmacokinetic: a GLP-1 analog engineered with modifications that extend its half-life far beyond any currently approved drug in the class, from semaglutide's ~7 days to a target that enables monthly and eventually quarterly dosing.
The rationale: weekly injection burden is significant for a disease requiring years of maintenance therapy. A quarterly injection changes the real-world treatment experience fundamentally — four clinic or pharmacy interactions per year vs fifty-two.
Intuition(The maintenance adherence problem)
Obesity treatment is indefinite — there's no course to complete. Weekly GLP-1 injections mean ~260 injections over five years for a patient who stays on therapy. Real-world adherence data shows significant dropout over that period. A quarterly injection over the same five years is 20 injections. That's not a marginal convenience difference — it's a different behavioral and logistical burden that should produce meaningfully different real-world adherence. If ASC30 reaches equivalent efficacy at quarterly dosing, the relevant comparison isn't just the weight loss number in a Phase 3 trial; it's the weight loss maintained over years of actual use.
Trial data
Phase 2 showed positive weight loss and glycemic results consistent with GLP-1R agonism at the dose levels tested. Specific efficacy numbers not yet fully public pending publication [verify — may have been published post-2025].
What to Expect
Based on GLP-1 mechanism and ultra-long-acting design:
Month 1 — Induction dose. Drug levels build over weeks rather than peaking and troughing weekly.
Month 2–3 — Steady-state drug levels. Weight loss expected to mirror semaglutide class at comparable exposure.
Quarterly maintenance — Four injections per year. Same mechanism as weekly drugs — the difference is entirely in the pharmacokinetic engineering.
Phase 3 design and full efficacy timeline not yet public.
Dosing and administration
Monthly subcutaneous injection during induction phase, targeting quarterly maintenance dosing. Specific titration schedule not yet public [verify against any published Phase 2 protocol].
Development status
| Milestone | Status |
|---|---|
| Phase 2 | Complete — positive results |
| Phase 3 design | Pending |
| FDA filing | Timeline not yet public |
Safety profile
Phase 2 safety consistent with GLP-1 class. No novel signals identified. The ultra-long half-life raises questions about how long side effects would persist if a patient needed to stop — a tolerability consideration distinct from weekly drugs. Full profile pending Phase 3.
Who It's For
- Adults with obesity (BMI ≥ 30 or ≥ 27 with weight-related conditions)
- People who want the efficacy of GLP-1 therapy with the lowest possible injection burden
- Long-term obesity treatment patients who've described weekly injections as their biggest adherence barrier
If quarterly dosing sounds right for you, ASC30 is a Phase 2 drug — not yet available. Check in with a provider about what's currently available while the quarterly class matures.
Summary(The ASC30 picture)
Same GLP-1R mechanism as semaglutide, dramatically longer dosing interval. The clinical bet is that quarterly adherence outperforms weekly adherence over multi-year obesity treatment, making equivalent Phase 3 efficacy better real-world efficacy. Phase 3 design and enrollment timeline is the pending question.
Petrelintide
At a glance
| Field | Details |
|---|---|
| Brand names | Not yet approved |
| Targets | AMYR (amylin receptor — no GLP-1R involvement) |
| Developer | Zealand Pharma / Roche |
| Modality | SC injection, once-weekly |
| Approval status | Phase 2 — [verify Phase 3 initiation status] |
| Key efficacy | ~10.7% weight loss (Phase 2) |
| Indications | Obesity (standalone and combination) |
User Sentiment
Petrelintide's patient community is small but specific — people who've tried GLP-1 drugs and stopped due to intolerable side effects, and their advocates. For that group, the reaction to a weight loss drug that doesn't touch GLP-1R at all is qualitatively different from how the broader community receives new GLP-1 entrants.
Example(What the community says)
In GLP-1 forums, "I can't tolerate semaglutide or tirzepatide due to nausea" is a recurring post that typically ends in frustration — there's nothing else available. When petrelintide data comes up in these threads, the response is disproportionately engaged for a Phase 2 drug most people haven't heard of, because it represents an answer to a question the class hasn't had an answer for.
How it works
Not a GLP-1 drug. Petrelintide is a synthetic amylin analog that activates the amylin receptor (AMYR) without touching GLP-1R. This makes it mechanistically independent from every other drug in this series.
Amylin is a pancreatic hormone co-secreted with insulin after meals. It signals satiety through the area postrema and nucleus tractus solitarius in the brainstem — distinct from GLP-1's hypothalamic pathway. Amylin analogs slow gastric emptying, suppress glucagon, and reduce food intake, but through signaling architecture that doesn't depend on GLP-1R activation.
Why this matters: GLP-1 drugs cause nausea and vomiting as a direct consequence of GLP-1R activation in the gut. A subset of patients discontinues therapy despite benefit because the GI side effects are intolerable. Petrelintide offers pharmacological weight management through a different circuit — for patients who can't use the rest of this drug class, it may be the only option.
It also positions as a combination partner: petrelintide added to a GLP-1 agonist hits two satiety pathways simultaneously, similar to CagriSema's approach but as separately prescribable drugs rather than a fixed-dose combination.
Important(The patient population this drug serves)
GLP-1 drugs cause nausea and vomiting through direct GLP-1R activation in the gut. This is not a dosing problem or a titration problem — it's a mechanistic consequence of activating GLP-1R at all. A subset of patients discontinues despite clinical benefit because GI side effects are intolerable at any dose. For those patients, every drug in the rest of this series is unavailable. Petrelintide is the only pharmacological weight loss option that doesn't touch GLP-1R at all — and for that patient population, 10.7% from a well-tolerated weekly injection is not a consolation prize. It's the only option.
Trial data
Phase 2 [verify trial name]: ~10.7% weight loss — lower than GLP-1 agonists and dual agonists. The relevant comparison isn't semaglutide, it's the current alternative for GLP-1-intolerant patients: nothing pharmacological. 10.7% from a well-tolerated weekly injection is meaningful for that population.
Combination trial data with GLP-1 agonist background therapy [verify — Zealand has indicated combination studies are planned or ongoing].
What to Expect
Based on Phase 2 data and amylin receptor mechanism:
Weeks 1–4 — GI side effects through the amylin pathway are distinct from GLP-1-mediated nausea. Milder in Phase 2 than GLP-1 comparators for most participants.
Month 2–3 — Appetite reduction and gastric slowing via amylin pathway. Slower weight loss curve than GLP-1 drugs — 10.7% is the Phase 2 number, not the starting-point number.
As a combination — For patients who can tolerate both, petrelintide + a GLP-1 drug hits two satiety circuits simultaneously (similar to CagriSema but as separate drugs).
Not yet available — Phase 2 complete, Phase 3 timeline pending.
Dosing and administration
Once-weekly subcutaneous injection. Specific dose range and titration schedule [verify — Phase 2 protocol details not fully public].
Development status
| Milestone | Status |
|---|---|
| Phase 2 (standalone) | Complete — ~10.7% weight loss |
| Phase 2 (combination with GLP-1) | [verify status] |
| Phase 3 initiation | [verify — expected 2025–2026] |
| Roche partnership scope | [verify — commercialization rights details] |
| FDA filing | Timeline not yet public |
Safety profile
Amylin receptor agonism causes GI side effects through a distinct mechanism from GLP-1R activation. Phase 2 GI profile appeared milder than GLP-1 class comparators [verify discontinuation rates], which is the core tolerability proposition for GLP-1-intolerant patients. No GLP-1-related cardiovascular or thyroid signals applicable. Novel safety signals specific to petrelintide in Phase 2 [verify safety summary].
Who It's For
- People who've stopped a GLP-1 drug due to intolerable GI side effects
- BMI ≥ 30 or ≥ 27 with weight-related conditions
- Anyone whose provider has said GLP-1 drugs "aren't for you" due to tolerability — this mechanism is different
- AMYR agonism works independently, so it can be combined with GLP-1 drugs for patients who tolerate both
If you've been told you can't take GLP-1 drugs, petrelintide is worth asking your provider about specifically. It's a different pathway entirely.
Summary(The petrelintide picture)
~10.7% weight loss from a mechanism with no GLP-1R involvement. Not competing with semaglutide — serving the patient population that can't tolerate semaglutide. The combination with GLP-1 background therapy is the growth path: two satiety circuits for patients who can tolerate both, similar to CagriSema but as separate prescribable components.