December 2026 Biotech Catalysts: 4 PDUFAs, 2 Readouts Ranked

November is the heavy month: COGT’s GIST PDUFA, BBIO’s BBP-418 in LGMD2i, and SVRA’s MOLBREEVI in aPAP all hit before Thanksgiving. December is the clean-up month. Companies that pushed their catalysts to year-end to get them into the current tax year populate the final four weeks. Four PDUFA dates and two Phase 3 data readouts land in December. Two of the six catalysts are ghosts, and one is a micro-cap lottery ticket trading at $1.13. Here is the tradeable rank.

Prior coverage of the October slate is in the October 2026 catalysts ranked piece and the November setup in the November 2026 catalysts ranked piece. The full Q4 picture is in the Q4 2026 FDA calendar.

1. COGT Bezuclastinib NonAdvSM PDUFA (Dec 30)

Cogent Biosciences ($7.24B market cap, $42.39) holds the December catalyst with the widest tradeable range. The FDA accepted the bezuclastinib NDA for NonAdvanced Systemic Mastocytosis (NonAdvSM) and set a December 30 PDUFA. This is the second bezuclastinib PDUFA: the GIST filing has its own earlier PDUFA, and both use the same drug with a shared clinical data package. The GIST setup is covered in the COGT bezuclastinib GIST PDUFA primer. The SUMMIT registrational trial demonstrated clear clinical benefit across all symptom domains in NonAdvSM. Cogent is planning dual launches of bezuclastinib in systemic mastocytosis and GIST.

The December 30 PDUFA has three structural advantages. First, it is the cleaner approval: NonAdvSM has fewer patients, less competitive density, and a more straightforward regulatory path than GIST. Second, it arrives after the GIST PDUFA resolves, so any GIST regulatory uncertainty is already priced by December. Third, two catalysts on the same drug create a re-rating staircase: if the GIST PDUFA succeeds, NonAdvSM becomes the second turn of the key rather than a standalone binary. If GIST fails, NonAdvSM becomes the last shot, and the stock drops 40-50% before this catalyst even arrives. The bull case is both approvals plus a launch in two indications with one commercial infrastructure.

Position for the GIST PDUFA first. If it succeeds, the NonAdvSM catalyst compounds the re-rating. If it fails, buying the dip for NonAdvSM is a 50/50 coin flip on a damaged story. Hold through both if already positioned. Do not initiate a new position in December without the GIST outcome.

ClinicalTrials.gov: SUMMIT trial

2. MIRM Maralixibat EXPAND Phase 3 Topline (Q4 2026)

Mirum Pharmaceuticals ($6.14B market cap, $100.65) completed enrollment in EXPAND in March 2026. The Phase 3 randomized, double-blind, placebo-controlled study evaluates LIVMARLI (maralixibat) for cholestatic pruritus in patients aged 6 months and older with rare cholestatic liver diseases, including biliary atresia. Topline data is expected Q4 2026. The primary endpoint is change in pruritus severity from baseline to Week 20.

This is a label expansion for a drug that is already approved and generating revenue. LIVMARLI is approved for cholestatic pruritus in Alagille syndrome (ALGS) and PFIC. EXPAND targets biliary atresia and other rare cholestatic liver diseases where no approved therapies exist for pruritus. The trial design and endpoints are detailed in the MIRM EXPAND biliary atresia primer. The IBAT mechanism is validated: block ileal bile acid reuptake, reduce serum bile acids, reduce pruritus. The question is whether the 20-week endpoint shows a statistically significant improvement across a basket of diseases with different underlying pathologies.

The risk is lower than a first-approval PDUFA because the drug is already on the market with a known safety profile. The upside is a label expansion into a population roughly 3-5x the size of the current ALGS/PFIC indications. At $6.14B market cap, Mirum is pricing in some probability of EXPAND success. A positive readout pushes the stock toward the $146 analyst target. A miss that shows no separation from placebo in the broader cholestatic population sends the stock back toward $70.

ClinicalTrials.gov: EXPAND (NCT06553768)

3. VNDA Imsidolimab GPP PDUFA (Dec 12)

Vanda Pharmaceuticals ($300M market cap, $5.00) has a BLA accepted for imsidolimab in generalized pustular psoriasis (GPP) with a December 12 PDUFA. Imsidolimab is a fully humanized IgG4 monoclonal antibody that inhibits IL-36 receptor signaling. The clinical data package and regulatory path are covered in the Vanda imsidolimab PDUFA primer. GPP is a rare, sometimes fatal autoinflammatory skin condition. The BLA is supported by a multi-regional clinical program.

At a $300M market cap, this is a binary event on a micro-cap. Vanda’s base business is declining: Q2 2026 revenue was $50.5M, down 4% year-over-year, with a net loss of $62.5M. The company is burning cash on a legacy psychiatry portfolio while the imsidolimab PDUFA is the only near-term upside catalyst. The bull case: GPP is an orphan indication with no IL-36 antagonist approved, and imsidolimab could generate $150-250M in peak sales. At a 3x peak sales multiple on a $300M market cap, approval re-rates the stock to $450-750M. The bear case: a CRL sends VNDA below $2, and the cash burn becomes existential.

The competitive context is thin. Boehringer Ingelheim’s spesolimab (IL-36R antibody) was approved in 2022 for GPP flares but is not approved in the US for chronic treatment. Imsidolimab targets the same pathway with a different antibody and may have a broader label. The FDA’s December 12 date is the binary.

This is a 1-2% position trade. The risk of a CRL is real, and Vanda’s remaining business does not support the current market cap without imsidolimab.

4. ADCT ZYNLONTA LOTIS-5 Full Data (Q4 2026)

ADC Therapeutics ($133M market cap, $1.13) already reported LOTIS-5 topline data on June 3, 2026. The full context is covered in the ADCT ZYNLONTA primer. The Phase 3 confirmatory trial of ZYNLONTA plus rituximab in relapsed/refractory DLBCL met its primary endpoint: PFS HR=0.73, p=0.008, with median PFS of 6.1 months vs 4.7 months for R-GemOx. CR rate was 39.5% vs 26.7%, median DoCR was 16.8 months vs 12.3 months. The full data, expected Q4 2026, includes subgroup analyses, biomarker data, and longer follow-up that will determine the regulatory path.

The problem: the stock did not move on the topline data. At $1.13 and a $133M market cap, the market is discounting two things. First, the safety signal: Grade 5 TEAEs in 13.2% of the ZYNLONTA arm vs 4.6% for R-GemOx, with the majority in patients aged 75 or older. Second, the PFS benefit was statistically significant but clinically modest (1.4-month improvement in median PFS). The full data needs to show that the survival tail extends for younger, fitter patients to support an sBLA filing. ADCT has $231M in cash (as of March 31), providing runway into 2028, so this is not a cash-runway trade. It is a regulatory-path trade.

The full data could support an sBLA filing that converts ZYNLONTA’s accelerated approval to full approval in second-line DLBCL. Or it could confirm that the safety signal limits the addressable population to younger patients, capping peak sales below $200M. At $133M market cap, either outcome moves the stock 50%+ in either direction. This is the highest-risk catalyst in December and the one to size smallest: 0.5-1% of a biotech portfolio.

ClinicalTrials.gov: LOTIS-5 (NCT04384484)

Ghost Catalysts

DCPH Tirabrutinib PCNSL PDUFA (Dec 18). Deciphera Pharmaceuticals was acquired by ONO Pharmaceutical in June 2024 for $2.4 billion and delisted from Nasdaq. The tirabrutinib NDA for relapsed/refractory primary CNS lymphoma is still pending with a December 18 PDUFA, supported by Phase 2 PROSPECT data showing 67% ORR and 44% CR. The catalyst is real, but the investable pure play does not exist in US markets: ONO trades on the Tokyo Stock Exchange. US investors cannot trade this PDUFA directly. Note it for the sector picture and move on.

SAOL SL1009 PDCD PDUFA (Dec 30). Saol Therapeutics is a private company. SL1009 (sodium dichloroacetate) is a class 2 resubmission for pyruvate dehydrogenase complex deficiency, an ultra-rare pediatric-onset mitochondrial disease with no approved therapies. The PDUFA is December 30. No public ticker means no tradeable catalyst. The approval would be a meaningful win for the PDCD patient community but is not investable.

Risks

December catalysts cluster at month-end: three of the four PDUFA dates land between December 12 and December 30, and both trial readouts are Q4. If the market sells off into year-end for tax-loss harvesting, the biotech sector gets hit across the board regardless of individual catalyst outcomes. The Q4 readout windows for ADCT and MIRM add timing risk: topline data could land at any point in the quarter, making options positioning difficult. The ghost catalysts, DCPH and SAOL, will generate headlines that move sector sentiment without a tradeable way to play them.

Verdict

Ranked by tradeable binary risk-reward: COGT (dual-catalyst setup but requires GIST outcome first), MIRM (lower risk, label expansion on an approved drug), VNDA (micro-cap binary, size small), ADCT (highest risk, topline already known, full data is a regulatory-path call). Ghost catalysts DCPH and SAOL are in the rear-view mirror.

If you are holding COGT through November, let the NonAdvSM catalyst ride as the second turn of the key. MIRM is the cleanest December trade: a Phase 3 readout on an approved drug in a new indication, with a known safety profile. VNDA and ADCT are position-sized at 1% or less; these are lottery tickets, not theses.