FSGS in Partial Remission, Plateaued: Does an SGLT2 Inhibitor Actually Have a Job Left to Do
A single patient in partial remission on immunosuppression whose proteinuria has stopped moving. The disagreement is less about whether an SGLT2 inhibitor could help than about what, specifically, it's actually being asked to do.
Kevin S. runs a small landscaping business and spent most of last spring managing a diagnosis he didn't have time for — biopsy-proven primary FSGS, found after routine bloodwork ordered for an unrelated knee injury turned up protein in his urine he'd never had checked before. Tacrolimus and maximized RAAS blockade brought his proteinuria down substantially, from 6 grams a day at diagnosis to 1.4 grams by month five, a real partial remission he was relieved to hear about. Three months later, at month eight, the number is still 1.4. It hasn't gotten worse. It also hasn't moved.
The evidence for adding an SGLT2 inhibitor here is real but comes from a slightly different angle than a straightforward 'does this help FSGS' question might suggest. DAPA-CKD and EMPA-KIDNEY both enrolled meaningful numbers of non-diabetic proteinuric CKD patients, including some with primary glomerular disease, and both found benefit on eGFR-slope and composite renal outcomes largely independent of diabetes status — a hemodynamic effect, reducing intraglomerular pressure through afferent arteriolar tubuloglomerular feedback, that has nothing to do with blood sugar and plausibly nothing to do with his disease's immune-mediated component either. That's an important distinction, because most of the supporting data for HIS specific situation — primary FSGS in partial immunologic remission, plateaued rather than actively worsening — comes from subgroup and secondary analyses within those larger trials, not a dedicated glomerular-disease-specific trial built around exactly his picture. Whether an SGLT2 inhibitor is worth adding depends less on whether it works in the abstract, which the broader trial evidence supports reasonably well, and more on what it's actually being asked to accomplish for him specifically — and whether a modest further proteinuria dip, if it happens, would mean anything different than it would in someone without his exact history.
In clinic, at the 8-month plateau
He's plateaued for three months on a regimen that got him from six grams a day to 1.4 and then stopped moving. DAPA-CKD and EMPA-KIDNEY both showed real benefit in non-diabetic proteinuric CKD, including glomerular disease subgroups, through a mechanism that's completely separate from what tacrolimus is doing. I'd add dapagliflozin now.
I'd hold off. The evidence for HIS specific situation — primary FSGS in partial remission, not actively worsening — comes from subgroups within those trials, not a dedicated study built around this picture. And if we add an SGLT2 inhibitor now, an expected early eGFR dip could look like either the drug working or something going wrong, and we won't have a clean way to tell which.
Waiting for a dedicated glomerular-disease trial that may be years away isn't obviously more conservative than acting on a real, if subgroup-derived, mechanistic signal in a patient who's stopped improving.
I think the interpretive worry is legitimate, but it's solvable without avoiding the drug. Add dapagliflozin, but be explicit — with him and in the chart — about what it's actually for: reducing intraglomerular pressure and offering long-term nephroprotection, not driving his FSGS further into immunologic remission. That's a different job than what tacrolimus is doing.
With that framing, a modest further proteinuria dip reads as the hemodynamic effect working as expected, not as evidence his underlying disease activity has changed — and if it doesn't dip further, that doesn't mean the immunosuppression has failed either. We get the plausible benefit without the ambiguity either of you is worried about.
Agreed: add dapagliflozin, explicitly framed to Kevin and documented in the chart as a hemodynamic/nephroprotective adjunct rather than an expectation of further immunologic remission. Proteinuria and eGFR rechecked at 4 weeks and 3 months, with the expected early eGFR dip discussed with him in advance so it isn't mistaken for worsening disease.