Forlong Biotechology to Present Preclinical Data from FL115, a novel interleukin-15 (IL-15) superagonist, and FL116, a PD-1/interleukin-18 (IL-18) bispecific antibody, at the 2026 AACR Annual Meeting

On March 17, 2026 Forlong Biotechnology, a clinical-stage biotech company focusing on developing transformative cytokine therapies for patients with severe unmet needs, reported that preclinical data from its IL-15 and IL-18 programs will be presented at the 2026 AACR (Free AACR Whitepaper) Annual Meeting held April 17-22, 2026 in San Diego, California.

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IL-15 Programs: FL115 is an engineered IL-15/IL15Rα-Fbody fusion protein and has demonstrated best-in-class (BIC) profile as monotherapy in heavily pre-treated patients with late stage solid tumors, of which 3 patients (~10%) remain on treatment and progression-free currently at 9, 11 and 20 months respectively. Poster 7932 further elucidated mechanism of action underlying FL115 BIC profile, with Cryo-EM analysis of FL115/FcRn/β2M complex. In vivo, RNA-Seq and single-cell transcriptomics revealed FL115 reshaped the tumor microenvironment by enhancing NK and T cells infiltration without not triggering activation of neutrophils and macrophage. Poster 6459 showed significant potential of FL115 subcutaneous formulation. Compared to IV injection, subcutaneous injection of FL115 resulted in drastic lowering of Cmax (up to 26.7×) with bioavailability at ~60% as well as good linearity in PK file. FL115 at approximately 9 mg per injection site in rabbits showed no significant gross skin irritation.

IL-18 Programs: using structural modeling with our AI-driven Intelligent Biomolecular Discovery Platform, we developed a series of engineered IL-18 variants (IL-18v) that fully escape IL-18BP neutralization while providing tunable IL-18R1 affinity, enabling customizable cytokine potency, as described in Poster 7779. Based on one such IL-18v, we developed FL116, a PD-1/interleukin-18 (IL-18) bispecific antibody.
Poster 1777 showed FL116 achieved potent anti-tumor activities and rechallenge-confirmed immune memory while maintaining systemic immune homeostasis in multiple tumor models, and re-ignited intratumoral cytotoxic immunity while reshaping the TME toward a highly inflamed, effector-dominant state.

"Forlong’s pipeline strategy is to modulate the immune system with precision via stimulation of specific immune cell subpopulation through engineered cytokines, providing new options for patients," said Dong Wei, Ph.D., Chief Executive Officer of Forlong Biotechnology, "IL-15 and IL-18 have long been believed to be attractive cytokines for cancer immunotherapy, and we appreciate the opportunity to present initial data of FL115 and FL116 programs to leading immuno-oncology experts in this prestigious forum."

Poster Details:

Title: A tunable interleukin-18 (IL-18) platform engineered for complete escape from the decoy receptor IL-18 binding protein (IL-18BP)
Poster Number: 7779
Date & Time: 4/22/2026

Title: FL116, a PD-1/IL-18 bispecific antibody, enables cis-activation of PD-1⁺ T cells and reshapes the suppressive tumor microenvironment (TME)
Poster Number: 1777
Date & Time: 4/20/2026

Title: FL115, a novel IL-15 superagonist rationally designed to minimize safety risks for cancer immunotherapy
Poster Number: 7932
Date & Time: 4/22/2026

Title: Development of FL115, a novel IL-15 superagonist, as subcutaneous injection for cancer immunotherapy
Poster Number: 6459
Date & Time: 4/21/2026

About FL-115

FL115 is an engineered IL-15/IL15Rα-Fbody fusion protein, aiming to enhance anti-tumor immunity via IL-15-mediated signaling on NK and CD8+ T cells while minimizing complexity from Fc. FL115 has demonstrated significant anti-tumor activities as a monotherapy or as part of combination therapy in vivo, and can be manufactured by a robust and efficient process with excellent product stability. Clinically, FL115 has demonstrated favorable safety profile and preliminary clinical responses as a monotherapy, and has the best-in-class potential to synergize with current and emerging T cell-targeting immunotherapies through combination therapy to significantly improve the treatment outcome for patients. It is currently being investigated in combination with Bacillus Calmette-Guérin (BCG) in a Phase 2 clinical trial to evaluate safety and preliminary efficacy in patients with nonmuscle invasive bladder cancer (NMIBC) and in combination with an anti-PD1 monoclonal antibody in a Phase 1b/2 clinical trial to evaluate safety and preliminary efficacy in patients with advanced solid tumors.

(Press release, Forlong Biotechnology, MAR 17, 2026, View Source [SID1234663652])

Olema Oncology to Present Preclinical Data for Palazestrant and OP-3136 at the 2026 AACR Annual Meeting

On March 17, 2026 Olema Pharmaceuticals, Inc. ("Olema" or "Olema Oncology", Nasdaq: OLMA), a clinical-stage biopharmaceutical company focused on the discovery, development, and commercialization of targeted therapies for breast cancer and beyond, reported it will present two preclinical posters at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting taking place April 17-22 in San Diego, California.

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Poster Presentation Details
Title: Palazestrant directly recruits the corepressor protein NCoR1 in vitro leading to complete antagonism of estrogen receptor alpha
Poster/Abstract: 2950
Session: Experimental and Molecular Therapeutics: Cellular Responses to Anticancer Drugs
Date/Time: April 20, 2026, from 2:00-5:00pm PT / 5:00pm-8:00pm ET

Title: Palazestrant, a CERAN, in combination with OP-3136, a KAT6 inhibitor, synergistically downregulates cell proliferation and metastasis related gene signatures
Poster/Abstract: 2949
Session: Experimental and Molecular Therapeutics: Cellular Responses to Anticancer Drugs
Date/Time: April 20, 2026, from 2:00pm-5:00pm PT / 5:00pm-8:00pm ET

Additional information can be found on the AACR (Free AACR Whitepaper) Annual Meeting website.

(Press release, Olema Oncology, MAR 17, 2026, View Source [SID1234663668])

Monte Rosa Therapeutics Announces Fourth Quarter and Full-Year 2025 Financial Results and Business Updates

On March 17, 2026 Monte Rosa Therapeutics, Inc. (Nasdaq: GLUE), a clinical-stage biotechnology company developing novel molecular glue degrader (MGD)-based medicines, reported business highlights and financial results for the fourth quarter and full year ended December 31, 2025.

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"Monte Rosa is now on the cusp of Phase 2 trial initiations for three clinical-stage programs, each targeting expansive opportunities. Strengthened by our recent capital raise, our cash runway now extends into 2029 and enables us to fund aggressive development plans for each of our programs through multiple anticipated readouts and value inflection points," said Markus Warmuth, M.D., Chief Executive Officer of Monte Rosa Therapeutics. "We recently presented clinical data from the Phase 1 study of our NEK7-directed MGD MRT-8102, demonstrating suppression of high-sensitivity C-reactive protein (hsCRP) at rates comparable to or better than those previously reported with biologic therapies, supporting the potential of MRT-8102 to be an oral best-in-class therapeutic among agents targeting the NLRP3/IL-1/IL-6 pathway. The unblinded SAD/MAD safety data announced today, combined with the recently announced 3-month results from our long-term cynomolgus (cyno) monkey toxicology study, further support the favorable safety/tolerability profile observed to date and wide therapeutic window of this drug candidate. In addition, today we released promising data from a cyno obesity study demonstrating substantial impact of NEK7 degradation on body weight and body fat composition, alone or in combination with semaglutide."

"Our preclinical and clinical data corroborate the important role of NEK7 in driving lipid and metabolite-induced inflammation and support further development of MRT-8102 in cardiovascular and cardiometabolic indications," said Filip Janku, M.D., Ph.D., Chief Medical Officer of Monte Rosa Therapeutics. "Dosing is underway in our expanded GFORCE-1 study in subjects with elevated cardiovascular disease (CVD) risk, with additional results expected in H2 2026, and we look forward to initiating multiple Phase 2 studies of MRT-8102, starting with an ASCVD study this year. We’re excited that our VAV1-directed MGD MRT-6160, in collaboration with Novartis, is advancing towards multiple Phase 2 study initiations in immune-mediated diseases. Additionally, based on the promising data from our Phase 1/2 study of MRT-2359 in combination with an AR inhibitor in mCRPC patients, we plan to initiate a new Phase 2 study this year to evaluate MRT-2359 in combination with the second-generation AR-inhibitor apalutamide in patients with AR mutations, a population with limited therapeutic options. We are very pleased to have entered into a supply agreement with Johnson & Johnson for the provision of apalutamide for this study."

RECENT HIGHLIGHTS

MRT-8102, NEK7-directed MGD for inflammatory diseases driven by the NLRP3 inflammasome, IL-1, and IL-6

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In January, Monte Rosa announced positive interim data from an ongoing Phase 1 clinical study evaluating MRT-8102. In subjects with elevated cardiovascular disease (CVD) risk, MRT-8102 demonstrated rapid and durable reductions in systemic inflammation. After four weeks of MRT-8102 administration, CRP levels decreased by 85%, and 94% of study participants achieved CRP levels below 2 mg/L, a threshold associated with reduced CVD risk. Single ascending dose (SAD) and multiple ascending dose (MAD) cohorts demonstrated deep and sustained NEK7 degradation at doses from 5 mg to 400 mg.
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Monte Rosa reported unblinded safety data from the SAD/MAD cohorts of the Phase 1 study. In a total of 88 participants treated, there were no serious adverse events (SAEs), and no treatment-emergent adverse events (AEs) over grade 2. Rates of treatment-emergent AEs were 22% in subjects treated with MRT-8102, compared with 32% in subjects treated with placebo. The most frequent treatment-emergent AE was headache, reported in 9% of participants treated with MRT-8102 and 9% of participants treated with placebo. The data support a broad therapeutic index for MRT-8102.
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Monte Rosa recently provided topline 3-month results from the ongoing long-term toxicology study in cynos. No test article-related findings were reported and the no observed adverse events level (NOAEL) was the highest dose tested, a dose approximately 200 – 300-fold over the projected human efficacious dose. These findings reinforce the favorable safety and tolerability profile observed to date in the ongoing Phase 1 clinical study of MRT-8102 and in the 28-day preclinical GLP toxicology studies.
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In a cyno model of high-fat diet-induced obesity, daily dosing of a NEK7 MGD for 11 weeks produced an approximately 8% reduction in body weight relative to vehicle-treated animals. When combined with the GLP-1 receptor agonist semaglutide, body weight loss exceeded 23% relative to the vehicle group (versus 17% for semaglutide monotherapy). These findings are consistent with similar studies conducted with MRT-8102, both alone and in combination with semaglutide, in a mouse model of high-fat diet-induced obesity. Notably, DEXA body composition analysis of the cynos revealed preferential reductions in central abdominal fat, a depot strongly associated withincreased metabolic risk, with proportionally greater loss compared with the gynoid fat depot and minimal impact on lean mass.
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As announced in January, the ongoing GFORCE-1 Study of MRT-8102 in subjects with elevated CVD risk has been expanded to multiple dose levels to accelerate development in atherosclerotic cardiovascular disease (ASCVD) with an anticipated readout in H2 2026. Dosing is now ongoing in the additional dose cohorts.
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Monte Rosa expects to initiate multiple Phase 2 studies of MRT-8102 in indications with high unmet need and strong biologic rationale for targeting the NLPR3/IL-1/IL-6 pathway:
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A study (GFORCE-2) of MRT-8102 in elevated CVD risk patients defined by Stage 3/4 chronic kidney disease and elevated CRP, expected to initiate in H2 2026, to evaluate the effect of MRT-8102 treatment for 12 weeks (plus open-label extension) on CRP levels, as well as effects on liver fat, liver inflammation, and obesity
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A study (GFORCE-3) of MRT-8102 in patients with gout flares, expected to initiate in Q4 2026 or Q1 2027
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A study (GFORCE-4) of MRT-8102 in patients with moderate to severe hidradenitis suppurativa, expected to initiate in H1 2027

MRT-6160, VAV1-directed MGD for immune-mediated conditions

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Advancement of MRT-6160 toward multiple Phase 2 studies in immune-mediated diseases is ongoing, in collaboration with Novartis. Results from the Phase 1, single ascending dose / multiple ascending dose (SAD/MAD) study in healthy volunteers (clinicaltrials.gov identifier NCT06597799) support a clear path into anticipated Phase 2 studies and broad potential applications in multiple immune-mediated diseases.
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In October, Monte Rosa presented additional supportive MRT-6160 preclinical data at ACR Convergence 2025. In a preclinical autoimmune disease model characterized by chronic inflammation, autoantibody production, and multi-organ involvement, administration of MRT-6160 resulted in broad activity across an array of disease markers, including attenuated autoantibody levels and reduced skin and kidney pathology.
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Monte Rosa has a global exclusive development and commercialization license agreement with Novartis to advance VAV1-directed MGDs, including MRT-6160. Monte Rosa is eligible to receive up to $2.1 billion in development, regulatory, and sales milestones, beginning upon initiation of Phase 2 studies. Novartis is responsible for conducting and funding Phase 2 studies. Monte Rosa will co-fund any Phase 3 clinical development and will share 30% of any profits and losses associated with the manufacturing and commercialization of MRT-6160 in the U.S., and is also eligible for tiered royalties on ex-U.S. net sales.

MRT-2359, GSPT1-directed MGD for metastatic CRPC

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In February, Monte Rosa announced additional interim data from an ongoing Phase 1/2 clinical study evaluating MRT-2359 in combination with enzalutamide in heavily pretreated patients with mCRPC. MRT-2359 is an investigational, orally bioavailable, GSPT1-directed MGD. PSA responses in patients with AR mutations expanded to 5 of 5 patients, with a 100% disease control rate, including 2 patients with RECIST partial responses and 3 with stable disease, all showing reductions in size of target lesions. Across all 15 evaluable patients, the overall RECIST disease control rate was 67%, and 10 of 15 patients showed tumor size reductions of target lesions. The combination of MRT-2359 and enzalutamide was generally well-tolerated with primarily Grade 1-2 AEs. There were no treatment discontinuations due to AEs. The data bolster the promising results shared in December, reinforcing MRT-2359’s potential in mCRPC.
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The Company plans to initiate a Phase 2 study in 2026 of up to 25 patients to efficiently assess the efficacy of MRT-2359 in combination with the second-generation AR inhibitor apalutamide in mCRPC patients with AR mutations, with potential to expand the study into additional patient subsets.
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In March, Monte Rosa announced it entered into a supply agreement with Johnson & Johnson to evaluate MRT-2359 in combination with ERLEADA (apalutamide) for the treatment of patients with mCRPC with androgen receptor (AR) mutations in its planned Phase 2 study.

Cyclin E1 and CDK2-directed MGD programs for solid tumors

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Monte Rosa continues to advance its cyclin E1 (CCNE1)- and CDK2-directed MGD programs for the treatment of CCNE1-amplified solid tumors and ER+ breast cancer toward clinical development. The Company expects to submit an IND application in 2026 for a cyclin E1-directed MGD.

Corporate

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In January, Monte Rosa closed an upsized underwritten public offering of 13,000,000 shares of its common stock, including the full exercise by the underwriters of their option to purchase an additional 1,875,000 shares, at a public offering price of $24.00 per share and, in lieu of common stock to certain investors, pre-funded warrants to purchase 1,375,000 shares of common stock at a public offering price of $23.9999 per pre-funded warrant, which represents the per share public offering price of each share of common stock less the $0.0001 per share exercise price for each pre-funded warrant. The gross proceeds to Monte Rosa from the offering, before deducting underwriting discounts and commissions and offering expenses, were approximately $345 million. All of the shares and pre-funded warrants in the offering were sold by Monte Rosa.
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In September 2025, Monte Rosa announced a second agreement to collaborate with Novartis to develop novel degraders for immune-mediated diseases. Monte Rosa’s publicly disclosed pipeline programs are outside the scope of this agreement. Under the terms of the agreement, Monte Rosa received an upfront payment of $120 million. Monte Rosa will also receive payments to maintain the options. In total deal value, Monte Rosa is eligible to receive up to $5.7 billion, including upfront, option maintenance, preclinical milestone, option exercise, and development, regulatory, and sales milestone payments across programs, as well as tiered royalties on global net sales in the high single to low double-digit range.
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In December 2025, Monte Rosa achieved a preclinical milestone under its strategic collaboration and license agreement with Roche, triggering a $7 million milestone payment to Monte Rosa.
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Monte Rosa reported two leadership team promotions: Magnus Walter, DPhil, to Chief Technology Officer, and Andrew Funderburk to Chief Investor Relations and Strategy Officer.

ANTICIPATED UPCOMING MILESTONES AND DEVELOPMENT PRIORITIES

Immunology and Inflammation disease programs

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Readout of MRT-8102 GFORCE-1 study in subjects with elevated CVD risk anticipated in H2 2026.
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Initiate multiple Phase 2 studies of MRT-8102, including in elevated CVD risk patients with Stage 3/4 chronic kidney disease in H2 2026, in gout flare patients in Q4 2026/Q1 2027, and in hidradenitis suppurativa patients in H1 2027.
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Submit an IND application for a second-generation NEK7-directed MGD in 2026.

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Monte Rosa expects its collaborator, Novartis, to initiate multiple Phase 2 studies of VAV1-directed MGD MRT-6160 in immune-mediated diseases in 2026.
Oncology programs

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Initiate the MODeFIRe-1 Phase 2 study of MRT-2359 in combination with apalutamide in mCRPC in Q3 2026.
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Submit an IND application for a cyclin E1-directed MGD in 2026.

FOURTH QUARTER AND FULL YEAR 2025 FINANCIAL RESULTS

Collaboration Revenue: Collaboration revenue for the fourth quarter of 2025 was $2.8 million, compared to $60.6 million for the fourth quarter of 2024, and $123.7 million for the year ended December 31, 2025, as compared to $75.6 million for the year ended December 31, 2024. Collaboration revenue represents amounts earned from the Company’s collaboration and license agreements with Roche and Novartis.

Research and Development (R&D) Expenses: R&D expenses for the fourth quarter of 2025 were $42.0 million, compared to $38.9 million for the fourth quarter of 2024, and $141.5 million for the year ended December 31, 2025, compared to $121.6 million for the year ended December 31, 2024. These increases were driven by increased spending during the year on our MRT-8102 program and on other development and discovery programs.

General and Administrative (G&A) Expenses: G&A expenses for the fourth quarter of 2025 were $10.5 million compared to $8.8 million for the fourth quarter of 2024, and $36.4 million for the year ended December 31, 2025, compared to $35.2 million for the year ended December 31, 2024. These increases, which include non-cash stock-based compensation, were driven by increased headcount and expenses in support of our growth and operations as a public company.

Net Loss: Net loss for the fourth quarter of 2025 was $46.1 million, compared to $13.4 million for the fourth quarter of 2024, and net loss for the year ended December 31, 2025, was $38.6 million, compared to $72.7 million for the year ended December 31, 2024.

Cash Position and Financial Guidance:

Cash, cash equivalents, restricted cash, and marketable securities as of December 31, 2025, were $382.1 million, compared to cash, cash equivalents, restricted cash, and marketable securities of $396.2 million as of September 30, 2025. The decrease of $14.1 million was primarily due to operational use of cash, partially offset by proceeds of $24.3 million from the sale of stock under our at-the-market program.

In January 2026, the Company closed an underwritten public equity offering of approximately $345.0 million aggregate gross proceeds. Aggregate net proceeds from the offering after deducting underwriting discounts and commissions and offering expenses are expected to be approximately $323.8 million.

Based on current cash, cash equivalents, restricted cash, and marketable securities, together with the proceeds from the 2026 Offering, the Company expects its cash and cash equivalents to be sufficient to fund planned operations and capital expenditures into 2029.

(Press release, Monte Rosa Therapeutics, MAR 17, 2026, View Source [SID1234663620])

Nuvalent to Present New Preclinical and Clinical Data for Zidesamtinib, an Investigational ROS1-Selective Inhibitor, at AACR Annual Meeting 2026

On March 17, 2026 Nuvalent, Inc. (Nasdaq: NUVL), a clinical-stage biopharmaceutical company focused on creating precisely targeted therapies for clinically proven kinase targets in cancer, reported the presentation of new data for zidesamtinib, an investigational ROS1-selective inhibitor, during two poster presentations at the American Association for Cancer Research (AACR) (Free AACR Whitepaper) Annual Meeting 2026, being held April 17-22 in San Diego. The posters will highlight clinical data from a subset of TKI pre-treated patients with ROS1-positive NSCLC treated in the ARROS-1 Phase 1/2 clinical trial and preclinical data further characterizing zidesamtinib’s brain penetrance and intracranial activity.

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Details of the poster presentations are as follows:

Title: Zidesamtinib in Patients with ROS1+ NSCLC Previously Treated with Repotrectinib or Taletrectinib
Presenting Author: Geoffrey Liu, M.Sc., M.D.1
Abstract Number: CT248
Session Title: Phase II Clinical Trials
Session Date and Time: Tuesday, April 21, 2026, 2:00-5:00 p.m. PT
Location: Poster Section 50
Poster Board Number: 13

Title: Zidesamtinib Has Differentiated Preclinical Brain Penetrance and Intracranial Activity Compared to Other ROS1 Inhibitors
Presenting Author: Anupong Tangpeerachaikul, Ph.D.2
Abstract Number: LB366
Session Title: Late-Breaking Research: Experimental and Molecular Therapeutics 3
Session Date and Time: Tuesday, April 21, 2026, 2:00-5:00 p.m. PT
Location: Poster Section 53
Poster Board Number: 23

1 Princess Margaret Hospital, Toronto, Ontario, Canada; 2 Nuvalent, Inc., Cambridge, MA, USA

About Zidesamtinib
Zidesamtinib is an investigational, brain-penetrant, ROS1-selective inhibitor created with the aim to overcome limitations observed with currently available ROS1 inhibitors. Zidesamtinib is designed to remain active in tumors that have developed resistance to currently available ROS1 inhibitors, including tumors with treatment-emergent ROS1 mutations such as G2032R. In addition, zidesamtinib is designed for central nervous system (CNS) penetrance to improve treatment options for patients with brain metastases, and to avoid inhibition of the structurally related tropomyosin receptor kinase (TRK) family. Together, these characteristics have the potential to avoid TRK-related CNS adverse events seen with dual TRK/ROS1 inhibitors and to drive deep, durable responses for patients across all lines of therapy.

Based on results for tyrosine kinase inhibitor (TKI) pre-treated patients with advanced ROS1-positive non-small cell lung cancer (NSCLC) enrolled in the global registrational ARROS-1 Phase 1/2 clinical trial, the U.S. Food and Drug Administration (FDA) has accepted for filing Nuvalent’s NDA submission for zidesamtinib for the treatment of adult patients with locally advanced or metastatic ROS1-positive NSCLC who received at least 1 prior ROS1 TKI. The application has been assigned a Prescription Drug User Fee Act (PDUFA) target action date of September 18, 2026. Zidesamtinib has received breakthrough therapy designation for the treatment of patients with ROS1-positive metastatic NSCLC who have been previously treated with 2 or more ROS1 TKIs and orphan drug designation for ROS1-positive NSCLC.

(Press release, Nuvalent, MAR 17, 2026, View Source [SID1234663637])

Pfizer Announces Positive Topline Phase 2 Results for Next-Generation CDK4 Inhibitor, Atirmociclib, in Second-Line Metastatic Breast Cancer

On March 17, 2026 Pfizer Inc. (NYSE: PFE) reported positive topline results from the randomized Phase 2 FOURLIGHT-1 study evaluating atirmociclib in combination with fulvestrant, versus fulvestrant or everolimus plus exemestane, in people with hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer (MBC) who had received prior cyclin-dependent kinase (CDK) 4/6 inhibitor-based treatment. The study met its primary endpoint, demonstrating a statistically significant and clinically meaningful improvement in progression-free survival (PFS) as assessed by the investigator [HR: 0.60 (95% CI: (0.440, 0.825)), p=0.0007].

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The PFS results were consistent across all prespecified subgroups, including performance status, menopausal status, presence of visceral disease, duration of treatment with prior CDK4/6 inhibitor (< or > 12 months), and regardless of prior CDK4/6 inhibitor received. More than 90% of patients initiated treatment with atirmociclib within three months of their last CDK4/6 inhibitor treatment. Overall survival (OS), a secondary endpoint, was not mature at the time of the analysis, with approximately 20% of participants having an event. These are the first randomized Phase 2 data in HR+ MBC for atirmociclib, an investigational, potential first-in-class CDK4 inhibitor.

"These results are especially encouraging given that the FOURLIGHT‑1 study enrolled patients whose disease had progressed soon after prior CDK4/6 inhibitor therapy, a difficult-to-treat population," said Jeff Legos, Chief Oncology Officer, Pfizer. "The strength of these data reinforces our confidence that atirmociclib may meaningfully differentiate from the CDK4/6 inhibitor class, the standard-of-care backbone in HR-positive breast cancer, with the potential for improved efficacy and tolerability. We are continuing to accelerate development of this next-generation cell cycle inhibitor in earlier lines of therapy where it may offer even greater benefit for patients."

In FOURLIGHT-1, atirmociclib demonstrated manageable safety and was well tolerated, with 6.4 percent of patients discontinuing atirmociclib due to treatment-emergent adverse events. Its safety profile was consistent with prior studies, and no new safety signals were identified. Detailed results will be submitted for presentation at a future medical meeting.

These findings support Pfizer’s strategy to advance atirmociclib in first-line and early-stage disease, where durable endocrine-based control has the potential to have the greatest impact. A Phase 3 registrational study for atirmociclib in the first-line metastatic setting is ongoing and results from a Phase 2 neoadjuvant study in early breast cancer will be shared at a future medical meeting.

About the FOURLIGHT-1 Trial

FOURLIGHT-1 (NCT06105632) is an interventional, open-label, randomized, multicenter Phase 2 study evaluating atirmociclib plus fulvestrant compared with fulvestrant or everolimus plus exemestane, in adults with hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative (HER2-) advanced or metastatic breast cancer (MBC). The trial enrolled 264 patients in 14 countries whose disease progressed after cyclin-dependent kinase (CDK) 4/6 inhibitor-based treatment. The primary endpoint was progression-free survival (PFS) as determined by investigator assessment. Secondary endpoints include overall survival, objective response, duration of response and clinical benefit response.

About Atirmociclib

Atirmociclib is an investigational oral inhibitor of cyclin-dependent kinase 4 (CDK4), a key regulator of the cell cycle that triggers cellular progression. It was conceptualized and discovered at Pfizer and is being developed for the treatment of hormone receptor (HR)-positive, human epidermal growth factor receptor 2-negative (HER2-) breast cancer.

(Press release, Pfizer, MAR 17, 2026, View Source [SID1234663653])