SARC041 Trial

Design - Phase 3 randomized, double-blind, placebo-controlled trial (n=108, 9 centers): abemaciclib (Verzenio, CDK4/6 inhibitor) vs placebo in advanced dedifferentiated liposarcoma (NCT04967521; SARC-sponsored, Lilly-funded; ASCO 2026 Plenary LBA2).

PFS (primary, MET) - Median 9.7 vs 1.5 months, HR 0.38 (90% CI 0.25-0.59), stratified log-rank p<0.001; 6-month PFS 60% vs 22%, 12-month PFS 39% vs 13%.

Overall survival (secondary) - Positive trend despite 85% placebo crossover: median OS not reached vs 25.5 months, HR 0.55 (95% CI 0.28-1.07), p=0.07.

Response - Objective response rate 9% (abemaciclib) vs 0% (placebo) - abemaciclib is distinct as the CDK4/6 inhibitor producing meaningful monotherapy responses in a disease dominated by disease stabilization.

Safety - Consistent with the abemaciclib class effects from monarchE and MONARCH 2/3 - predominantly low-grade diarrhea, neutropenia and fatigue.

Regulatory / sponsor - Investigational in DDLPS; abemaciclib (Verzenio) approved in HR+/HER2- breast. Lilly plans a regulatory submission. Sponsor SARC.

Compiled and reviewed by the KOL Pulse research team, led by Brian Shields, Founder, KOL Pulse. Last updated July 21, 2026.

Progression-Free Survival (Primary Endpoint)

Abemaciclib met the primary endpoint with a median PFS of 9.7 months versus 1.5 months for placebo — hazard ratio 0.38 (90% CI 0.25–0.59), stratified log-rank p<0.001. The benefit held across landmark timepoints: 6-month PFS 60% vs 22% and 12-month PFS 39% vs 13%. This is the first positive Phase 3 readout for any systemic therapy in dedifferentiated liposarcoma. An exploratory analysis by prior treatment showed a larger effect in treatment-naive patients (median PFS 16.4 months with no prior lines vs 5.3 months with ≥1 prior line; p=0.029).

Overall Survival (Secondary Endpoint)

A positive OS trend favored abemaciclib despite 85% of placebo patients crossing over to open-label abemaciclib at progression. Median OS was not reached with abemaciclib versus 25.5 months for placebo — HR 0.55 (95% CI 0.28–1.07), stratified log-rank p=0.07. Landmark OS favored abemaciclib at 12 months (85% vs 71%) and 24 months (72% vs 51%). The OS comparison did not cross the significance threshold — expected given the high crossover — but the consistent direction reinforces the PFS benefit.

Objective Response & Crossover

Objective response rate was 9% with abemaciclib versus 0% with placebo, consistent with abemaciclib's distinction as the only CDK4/6 inhibitor producing meaningful monotherapy responses in DDLPS (a disease dominated by disease stabilization rather than tumor shrinkage). Among the 46 placebo patients (85%) who crossed over to abemaciclib at progression, post-crossover median PFS was 3.4 months with a 4% response rate — demonstrating activity even in a more heavily pretreated, progressing population.

Clinical Context — DDLPS Disease Burden

Dedifferentiated liposarcoma most commonly arises in the retroperitoneum or abdomen. Recurrent/metastatic disease has historically had no standard-of-care systemic therapy — chemotherapy provides modest, short-lived benefit, and prior CDK4/6i trials (palbociclib, ribociclib) showed primarily stable disease. The earlier Phase 2 abemaciclib monotherapy study (Dickson et al., 30 patients) reported median PFS of 30-33 weeks and 12-week PFS of 76.7%, providing the rationale for SARC041.

Mechanism of Action — CDK4 Inhibition

Abemaciclib is an oral selective CDK4/6 inhibitor (vs the broader CDK4/6 class — palbociclib, ribociclib). DDLPS is characterized by amplification of the 12q13-15 region containing CDK4 and MDM2, making CDK4 a near-universal oncogenic driver. Inhibition disrupts cell-cycle progression and, per correlative work, induces tumor-cell senescence with secondary immune infiltration (CD4+ TILs). Among the three approved CDK4/6 inhibitors, abemaciclib is unique in producing meaningful monotherapy objective responses.

Safety & Tolerability (Expected Profile)

The Plenary safety profile was consistent with the well-characterized abemaciclib class effects from monarchE (adjuvant breast) and MONARCH 2/3 (metastatic breast): predominantly low-grade diarrhea, neutropenia, and fatigue. Grade ≥3 neutropenia rate in prior abemaciclib monotherapy trials runs in the 20-25% range, with median time-to-onset ~29-37 days; dose reduction to 100 mg has not historically compromised efficacy. No new safety signals were reported in the earlier DDLPS Phase 2. Full DDLPS-specific safety detail is in the Plenary deck and the upcoming publication.

Regulatory & Commercial Implications

Verzenio (abemaciclib) is currently approved by FDA in HR+/HER2- early and metastatic breast cancer. SARC041 provides the first randomized Phase 3 evidence of a CDK4/6 inhibitor benefit in any sarcoma subtype. Eli Lilly has stated the SARC041 data will support a regulatory submission for an expanded DDLPS indication. The Plenary selection (LBA2) — alongside LIBRETTO-432, HARMONi-6, RASolute 302, and PROTEUS — signals ASCO's view of the study as practice-changing for a rare disease with no current standard of care.

What is the SARC041 trial?

SARC041 (NCT04967521) is a Phase 3, randomized, double-blind, placebo-controlled trial (108 patients across 9 centers) sponsored by the Sarcoma Alliance for Research through Collaboration and funded by Eli Lilly. It tested the CDK4/6 inhibitor abemaciclib (Verzenio) versus placebo in advanced dedifferentiated liposarcoma, a sarcoma subtype characterized by amplification of the CDK4-containing 12q13-15 region. It was presented as an ASCO 2026 Plenary (LBA2).

What did SARC041 show?

Abemaciclib met the primary endpoint with a median progression-free survival of 9.7 versus 1.5 months for placebo (hazard ratio 0.38, p<0.001), with 6-month PFS of 60% versus 22% and 12-month PFS of 39% versus 13%. Overall survival trended in favor of abemaciclib (median not reached versus 25.5 months) despite 85% of placebo patients crossing over. Objective response rate was 9% versus 0%. It is the first positive Phase 3 trial in dedifferentiated liposarcoma.

Is abemaciclib (Verzenio) FDA approved for sarcoma?

No. Abemaciclib is not FDA-approved for dedifferentiated liposarcoma or any sarcoma; its use in SARC041 is investigational. Abemaciclib (Verzenio) is FDA-approved in HR-positive, HER2-negative early and metastatic breast cancer. Eli Lilly has stated the SARC041 results will support a regulatory submission for an expanded indication.

What is the safety profile of abemaciclib in SARC041?

The safety profile was consistent with the well-characterized abemaciclib class effects seen in the breast-cancer trials monarchE and MONARCH 2/3 - predominantly low-grade diarrhea, neutropenia and fatigue. No new safety signals specific to the sarcoma population were highlighted at the Plenary presentation.

Why is SARC041 important for liposarcoma?

Recurrent or metastatic dedifferentiated liposarcoma has historically had no standard-of-care systemic therapy, and prior CDK4/6 inhibitors (palbociclib, ribociclib) showed mainly disease stabilization. SARC041 is the first randomized Phase 3 to demonstrate a CDK4/6 inhibitor benefit in any sarcoma subtype, providing potential practice-changing evidence for a disease with high unmet need.